Leiths School of Food and Wine
52 recipes
Published by
Quadrille Publishing
Peter Cassidy

This chapter will give you all the knowledge you need to select really fresh fish, including some of the less commonly used species, and to prepare and cook it using a variety of methods. All you need to do is master some simple fishmongering skills and techniques. A basic understanding of the classification of fish is helpful when it comes to choosing particular fish, and will enable you to apply appropriate preparation methods. Once you know how to prepare flat and round varieties of white fish and large and small round oily fish, as well as smoked fish and delicate cured fish, you will find it easy to substitute one species for another.

Buying fish

It is important to buy fish which has a sustainable supply, and every cook should know how to select a more plentiful variety in place of one that is becoming over-fished. The list of MSC (Marine Stewardship Council) approved fish changes as stocks recover or are overfished, so check their list regularly and make sure that you buy only MSC certified or approved fish. Flavour combinations tend to work well with similar types of fish, so experimenting with new varieties can produce delicious new recipes.

Identifying the freshest fish, whether whole or in fillets, is a useful and important skill.

Choosing whole fish

Smell: Fresh fish should smell of the sea, not have an unpleasant ‘fishy’ odour.

Natural slime: Fish should be shiny with a natural moist slime and no dry areas.

Scales: These should all be intact, with no dry or scale-free patches.

Eyes: These should be clear and prominent, bulging not sunken.

Fins: These should all be intact and perky, not dry, limp and broken.

Gills: These should be a bright pink or red, not grey or brown or discolouring.

Touch: Fish should be firm to the touch, not soft or flabby.

Selecting fish fillets

With fewer indicators than for a whole fish, it is harder to tell if fish fillets are fresh. It is also difficult to examine them properly if they are wrapped. However, there are a few signs to look out for: fillets should be bright and shiny, with a white or pale white or pink colour depending on the type of fish, and no discolouration. The flesh should be firm to the touch, not soft, and your finger should not leave an indentation when you press it. As for whole fish, fillets should smell fresh, of the sea rather than overtly ‘fishy’.

Freshwater and farmed fish

Freshwater and farmed fish can be harvested when needed and so can be fresher when purchased than wild sea fish. However, the fish tend to be caught younger and smaller, which does not allow them time to develop the flavour of wild fish. Farmed fish may be reared in small, confined areas, so fins can be stunted and broken; they can also be fattier than wild fish.

Fish classification and identification

There are many ways to classify fish, but the most important distinctions for the cook are whether the fish is flat or round, and white or oily. This determines the best technique to use in preparing the fish, the most appropriate cooking method and which combinations of flavour will work well with the fish.

Flat fish live and feed on or near the sea bed and range from small dabs to the huge turbot. Round fish live both on or near the sea bed, and through the middle and surface levels of the sea, and include cod, salmon, mackerel and herring.

In white fish the oils are concentrated in the liver, whereas in oily fish the oils are spread throughout the fish. These are the beneficial omega-3 oils and oily fish should be eaten at least a couple of times a week as part of a well-balanced diet.

Storing fish

Ideally fish should be used the day you buy it. To store briefly, wrap in cling film and place in a shallow tray in the bottom of the fridge (generally the coldest part).

Try to avoid freezing fish. If you do have to freeze it, wrap it very closely in cling film, excluding any air pockets and use it as soon as you can, as the quality of frozen fish deteriorates over prolonged periods of time. However, fish that is frozen as soon as it is caught can be in a better condition than fresh, depending on how long it has taken to get from the sea to your kitchen. It is best to defrost fish in the fridge, on a tray covered with kitchen paper to absorb any water.

Cooking fish

Fish very rarely needs long, slow cooking as its flesh is made up of short, delicate muscle fibres and connective tissue that break down very quickly on cooking. Fish can be successfully pan-fried, baked, roasted and deep-fried. For more delicate results, it can be poached or steamed.

Assessing whether fish is cooked

While it is feasible to use a thermometer and calculations that involve measuring the thickness of the fillet, it is easier and perfectly possible to use your senses to judge whether fish is cooked; guidance is included in the individual recipes. Great care must be taken to avoid overcooking fish, which causes it to fall apart, lose flavour and become tough and dry.

Flat fish

All flat fish are classified as white fish, because the greatest concentration of their fat is contained in the liver, which ensures they have lean, white flesh. Although similar in appearance, each species has a distinctive flavour. They include plaice, lemon and Dover sole, brill, turbot, flounder and dabs. Skates and rays, with their cartilaginous (soft) frames, are also flat fish, although prepared differently as it is their ‘wings’ that are prized in cooking.

Filleting a flat fish

This method removes 4 fillets from a flat fish. Fishmongers will often remove a whole side, so 2 double fillets from each flat fish. What is important is that you develop a method of filleting that you are comfortable with, that you use your knife safely and that you waste as little fish as possible. It is essential to use a very sharp knife, preferably with a long flexible blade.

First rinse the fish under cold water and dry with kitchen paper. Fish have a natural slime and rinsing it off makes it easier to handle.

1. Place the fish on a board, tail end towards you and darker side uppermost. Using a fish filleting knife, make an incision along the natural line running down the middle of the fish, from behind the head down to the tail.

2. Make a small cut across the top of the tail.

3. Make a cut from behind the head down to the edge of the fish behind the gill and head on both sides.

4. Release a little of one of the fillets from the back bone, the full length of the fish. Then, using the flexibility and length of a fish filleting knife and long strokes, carefully release the fillet away from the skeleton. Try to keep the knife as flat against the bone as possible. You should hear a rasping sound as the knife blade works its way across the bones.

5. As the knife approaches the edge, lift up the fillet to make it easier to see what you are doing.

6. When you reach the frill, either grip the edge of the skin of the fillet and pull the fillet firmly away from the body, taking care not to damage the flesh, or cut the fillet away from the frill and main body of the fish.

7. Repeat with the remaining top fillet. You need to ensure the knife blade is on the right side of the little vertical back bone before starting to remove the fillet.

8. Turn the fish over and repeat the process on the pale underside. The skin here is a little tougher.

9. Once you have removed all 4 fillets, put them aside ready to skin or cook with the skin on. Remove the head from the frame, bend the frame to break the bone and cut through the breaks, then rinse the bones and use for stock, or freeze for later use.

Note: Now scrape the board to get rid of any loose bits of fish and rinse well under cold water, then wash well under hot water and detergent. Dry well.

Skinning a flat fish

If necessary, first wipe over the fillets with kitchen paper to ensure they are dry.

1. Place a fillet skin side down on the board with the narrow end towards you. There is a natural break between the fillet and the frill. Use the tip of a finger to identify and open this. Cut down this line to remove the frill on all 4 fillets. As you become more confident with your fish filleting and skinning skills, it may not be necessary to remove the frill first; it will naturally come away as the fillet is skinned.

2. Take a little salt in the fingers of your non-knife hand and hold onto the end of the fillet tightly. Insert the knife between the skin and flesh, just in front of your fingers, at a 30–40° angle.

3. Now, holding firmly onto the skin, move the knife decisively to the left and right using an exaggerated sawing action, while maintaining a firm pressure with the knife on the fish skin, to start to release the flesh from the skin.

4. As you release more flesh adjust the position of the fingers holding the skin closer to the unreleased flesh. It is important to firmly press the knife blade against the skin, which is against the board. Work your way up the fillet like this, releasing the flesh as a whole fillet. Take care not to hold the knife blade too vertically or you will cut through the skin, but too flat against the skin and you will leave flesh on the skin; it takes some practice.

5. Repeat with the remaining 3 fillets. Wipe down the board with kitchen paper and lay the fillets on the board. Once skinned, trim the fillets as necessary, without wasting fish.

6. Feel the fillets all over for bones. Usually this method of filleting leaves the fillets bone free, but it is always good to check. Remove any small bones that you find with kitchen tweezers. The fillets are now ready to use.

Note: When skinning, we find it easier to move the knife hand back and forwards, but, as with filleting, if you find it more comfortable to hold your knife hand steady and move the hand holding the skin from side to side, use this technique. You should adopt the method that feels the most comfortable and safest for you, and one that prevents wastage. It is easier to remove the darker skin from the fillets than the paler skin.


Generally, when referring to fish, the non-skin side (the bone side) is the best looking side once cooked and will become the presentation side. The skin side generally has a little brown flesh under the skin which is evident after skinning. It also often has a ‘V’ pattern. You should cook the non-skin presentation side first, as this will almost always end up being the best looking and most appetising side.

When folding fillets, fold them skin side inwards, bone side outwards.

There are always exceptions. When grilling, you should grill the non-skin side last, as the second side of a grilled fillet is generally the better looking.

Braising and baking

Here the fish is cooked in the oven, covered either with a tight-fitting lid or wrapped in foil, greaseproof paper or baking parchment. A small amount of liquid is added, which helps to retain moisture in the fish, and flavour the cooking liquor, which is more often than not used for a sauce to serve with the fish.

A gentle method of cooking, braising is often used to cook large pieces of meaty fish, such as tuna, or for shellfish such squid or octopus. It is a good alternative to poaching, and in both methods no colour is achieved on the fish.

Sometimes the term baking is used interchangeably with roasting, where fish is cooked in a hot oven and browned in the process.


This is a very gentle method of cooking fish, and ideal for healthier diets as it requires no additional fat. Poaching involves submerging the fish in liquid and cooking either on the hob or in the oven at a very low heat, so there is very little movement of liquid. It is suitable for fish that can easily break up if subjected to a lot of movement. It can help to retain moisture in fish and the poaching liquor is often used to make a sauce to accompany the fish.

Ideally, the poaching liquid should be cool before the fish is added and the heat then increased slowly to ensure even cooking. If placed in a hot liquid, the outside of the fish cooks quickly, and by the time the inside is cooked, the outside can be overcooked. Larger pieces of fish or whole fish are best suited to poaching. To poach a large, whole fish such as a salmon you will need either a fish kettle or a large roasting tin.

The poaching liquid can be stock, milk or a court bouillon; adding flavourings to the poaching liquid further benefits the fish.


Steaming is perfect for cooking delicate pieces of fish or small, whole fish. It is a very healthy method, as it uses no fat and there is minimal vitamin and mineral loss, because the fish sits over, not in, the liquid when it is being steamed. The liquid used to steam the fish can be flavoured with spices and aromatics to help flavour the fish.

If you do not have a proper steamer, you can use a large saucepan with a trivet in the bottom, with the fish on a small heatproof plate placed on the trivet. Alternatively, bamboo steamers of various sizes are widely available. When using a bamboo steamer, place the fish on a square of non-stick baking parchment to avoid the bamboo absorbing the fish flavour.

Always ensure the steamer has a tight-fitting lid so little or no steam can escape. The liquid should be kept at a constant generous simmer to ensure enough steam is created to cook the fish quickly.

Skinning and preparing a flat fish before cooking, to be served on the bone

Small flat fish can be skinned prior to cooking whole. Note that flat fish are often sold already gutted, but sometimes the roe is left in the gut area.

First rinse the fish under cold water and dry with kitchen paper.

1. Place the fish on a board with the tail end towards you. Using a small knife, make a shallow cut just above the tail.

2. Using the tip of a fingernail, push the skin up from the flesh a little, particularly over the frill. Insert a fingertip between the skin and the frill and release the skin up the entire side of the fish. Repeat on the other side.

3. Salt the fingers to get a good grip on the skin and hold the tail tightly with the fingers of one hand. With the other hand, hold the released skin firmly at the tail end and pull away from you horizontally. Repeat the skinning process on the other side.

4. Check the cavity and gut the fish if necessary; the roe and gut can be pulled out of the belly from behind the gills. Alternatively, release the flesh along the frill line on both sides to open the belly area up. (If serving with the head on, remove the gills at this stage.) Rinse the fish under cold water to clean the belly area, then dry. The fish is now ready to cook.

5. After cooking and while the fish is still on its baking tray, use a small knife to draw the frill bones away from between both fillets on each side of the fish, leaving just the fillets on the bone. Remove the head at this stage (unless you prefer to leave it on).

6. Carefully lift the fish onto a plate to serve.


When grilling fish, you need to heat the grill to its hottest setting to achieve colour quickly, while ensuring the fish retains moisture. It can take up to about 10 minutes for a grill to heat properly. Basting the fish as it grills will also help to brown it and keep it moist. Once it is browned, you may need to lower the grill shelf to allow the fish to cook through.

Grilling is best suited to small pieces, or fillets, of fish. Remove the fish from the fridge ahead of grilling to bring it up to room temperature, or the browning can be so quick that the centre remains cold. If the fillets are thin they will probably not need to be turned over, particularly if using a metal baking sheet, as the heat from the grill will be conducted to the underside of the fish.

If the fish is thick (more than 2–3 cm), the best option to avoid burning the fish is to grill it until browned, then transfer it to an oven preheated to 180ºC to finish the cooking. This is particularly useful if you are cooking a large quantity of fish in batches.

When grilling fish with the skin on, score the skin several times with a very sharp knife to prevent it from buckling under the grill.


Pan-frying is a very quick method of cooking small pieces of fish in a minimal quantity of fat (butter and/or oil) and helps to add colour and texture to the dish, creating a good brown crust on the fish. Butter provides flavour but burns easily; adding a little oil helps to raise the temperature at which butter burns, allowing a longer cooking time.

A non-stick pan is ideal for pan-frying, as the skin and fish are not damaged by sticking to the pan. If you don’t have a non-stick pan, a pan can be ‘proved’, or made non-stick.

Use a large, shallow pan so that the fish can be easily manoeuvred, and avoid overcrowding the pan by trying to fry too much at a time.

Thin fillets will generally need an equal cooking time on both sides, but if the fillet is thick, most of the cooking can be done on the presentation side, then turned over and briefly cooked presentation side uppermost or transferred to the oven (if using an ovenproof frying pan) to finish the cooking at 180ºC.


This method of cooking is best for larger pieces of fish or whole fish, particularly when the fish is larger than any of your frying pans. Roasting involves heating the oven to a high heat to achieve colour and to cook the fish through quickly. Fish can be basted while roasting to ensure it stays moist.

For smaller cuts or fillets, fish is often pan-fried first to achieve browning, then roasted in the oven to finish the cooking.

Preparing a flat fish to cook whole, skin on and on the bone

1. Rinse the fish under cold water, dry with kitchen paper and place on a board. Remove the gills.

2. Check the cavity for guts and roe. More often than not, flat fish will already have been gutted, but if not, make an incision behind the gills.

3. Pull the guts and roe out of the belly; make an incision along the edge of the fillet on the join with the frill to release them if necessary. Rinse the fish under cold water again and dry.


This quick method of cooking at a very high heat is best for tiny whole fish, such as whitebait, and small pieces or fillets of larger fish. Flavourless oils, such as a vegetable or groundnut oil, are best and should not be re-used, unless for fish frying once or twice more, as the flavour of the fish will transfer to the oil.

Coating fish in a wet batter or dry crumb before deep-frying protects the fish from the high heat of the oil and helps retain its moisture and tenderness, resulting in a pleasing contrast in texture between the crisp coating and the softness of the fish underneath. Dusting the fish in flour before coating in a wet batter ensures the batter adheres to the fish. For a dry crumb, the fish is first dusted in flour, then egg, then crumb to ensure an even coating.

When deep-frying small pieces of coated fish, cook only a few at a time, as the oil temperature drops very quickly once cool food is placed in it, and deep-frying at a low temperature causes the coating to soak up oil, resulting in greasy food.

For more information on the technique of deep-frying, including testing the temperature of the oil if your deep-fat fryer is not thermostatically controlled and safety issues.

Round fish

Round fish are characterised by the back bone running along the length of the body with a single fillet located on either side. The flesh can be oily or white. There are many white-fleshed species, including sea bass, cod, haddock, pollock, bream, John Dory and mullet.

Most white-fleshed round fish can be cooked whole, or filleted for easier serving. The delicate flavour of fish means that it can be prepared with little more than a squeeze of lemon and drizzle of olive oil, as long as it is not overcooked. However, its relatively mild character means that it can also happily take on different flavour combinations, and many round fish pair well with the bold flavours of Mediterranean cooking or the aromatics and spices of Asia.

Descaling and gutting a round fish

1. To descale the fish, put it inside a large plastic bag, head first (to prevent the scales flying everywhere as you remove them). Using a fish filleting knife upside down (the non-sharp side against the fish) and holding onto the fish tail, push backwards towards the head and the scales should flip off. Turn the fish over and repeat on the second side.

2. Once the scales are removed, take the fish out of the plastic bag and rinse under cold running water to remove any loose scales. Pat dry with kitchen paper.

3. Using a pair of kitchen scissors, cut off all the fins except the dorsal fin (in the middle on the back). The tail can be trimmed into a ‘V’ shape if you like.

4. Remove the gills on both sides, by opening the gill flaps and cutting round the back of the gills towards the body of the fish from the top of the fish down towards the belly.

5. To gut the fish, place one hand on the uppermost side of the fish to help keep the belly skin taut and insert the point of a filleting knife into the vent hole.

6. Cut up the middle of the belly of the fish to just behind the head. Don’t push too deep with the knife or the guts will be cut into unnecessarily.

7. Open the belly and pull away the guts, including the heart and liver tucked just behind the head. You might need to snip these out using a pair of scissors.

8. Once the guts are removed, break the blood line with the handle of a teaspoon and scrape out all the blood under the back bone.

9. Rinse the fish and belly area well under cold running water to remove any blood. Wipe the fish out with kitchen paper. It is now ready to cook whole or to fillet.

Filleting a round fish

Although with practice it is possible to fillet a round fish without removing its innards, gutting it first ensures the fillets are not contaminated by guts, should the knife cut through bones into the guts when filleting.

1. Descale and gut the fish. Make a cut across the fish at an angle, below the gill flap and fin to the belly.

2. Keeping one hand pressing down firmly on the side of the fish, make a cut from behind the head along the top of the fish down its back, on top of the dorsal fin, to the tail. Use the whole back of the knife to do this, not just the point.

3. Using long strokes of the knife, release the top fillet, making sure the knife blade runs horizontally as closely as possible along the bones. Try to ensure that no fish is left on the bone. Take care coming to and over the back bone; make sure you are on top of the bone rather than under it. Also take care over the belly bones that they are not cut through or fish left on the bone.

4. Once you are over the belly bones, the fillet will come away cleanly. Put the fillet to one side while you work on the second fillet.

5. The second fillet is a little trickier to remove. Start with the exposed bone uppermost, and again make a cut from just behind the head parallel to the cut made for the first fillet, but this time work your knife just beneath the dorsal fin, cleanly cutting along the backbone from head to tail.

6. Now turn the fish over and, if you are able to, hang the fish’s head over the side of the board to allow the main body of the fish to be flat against the board. Proceed as for the first fillet. Once the second fillet has been removed the frame can be discarded, or if it is a white fish, you can remove the head, rinse the frame and keep it for stock.

7. Place the fish fillets on a plate while you wash and dry the board. Put the fillets back on the board. Trim any excess fatty skin from the belly side, but keep the fillets as natural a shape as possible.

8. Run the tip of your finger along the middle of the fillet and you will feel the bones running close through the thickest part of the fillet. It is imperative that these are removed before further preparation or cooking.

9. Using a pair of kitchen tweezers, carefully pick out each bone, supporting the fillet as you do, to ensure only the bone and not fish is removed. Repeat with the remaining fillets. The fillets are now ready either for skinning (as for flat fish fillets) or for cooking.

Oily fish

All oily fish are also round fish. As the fat is distributed through the flesh of oily fish, they have a stronger and sometimes more distinctive flavour than white fish. However, this also means that they often work well in bold flavour pairings. The rich flavour of mackerel is complemented by the acidity and sweetness of slow-roasted tomatoes, while the firm texture and robust flavour of tuna makes it an ideal partner for soy, ginger and coriander, or a punchy pesto. Containing essential omega-3 fatty acids, oily fish have the double benefit of being both healthy and delicious.

How to noisette a cutlet of fish

This useful technique is employed to bone a fish cutlet, to create a noisette of fish that is a little easier to cook and looks more attractive.

1. Place the cutlet on a board and carefully release the skin from the ends to halfway up each side, but do not detach completely.

2. Keeping the skin intact at the top of the cutlet, cut down on each side of the bone, then around the circular back bone, continuing down the inside to remove the bone.

3. Using kitchen tweezers, pin-bone the remaining fish; the pin bones are found through the widest section of each half of the cutlet.

4. Take one skinned end and tuck it in the place where the bone was, so it effectively replaces the bone. Wrap the other end around the outside to create a disc of fish.

5. Wrap the loose skin around the noisette to enclose it and tie with string to secure.

6. Place on a large plate or tray and repeat with any remaining cutlets, then weight the cutlets lightly to set their shape. Remove the string after cooking, before serving.

Boning smaller round fish

This technique is suitable for sardines, herring and other small round fish.

First descale and gut the fish to prepare them for cooking whole, but trim off the dorsal fin too. Rinse the fish under cold running water and pat dry with kitchen paper.

1. Lay the fish on a board and, at the vent hole, cut towards the tail, opening the 2 fillets completely.

2. Open the belly area and place the fish skin side up, so the fish fillets lie flesh side against the board.

3. Run your thumb from the tail to just behind the head along the back bone of the fish, which will help to release the bone.

4. Turn the fish over so it is skin side down and, using a pair of scissors, snip the bone behind the head and at the tail.

5. Supporting the fish at the head end, carefully pull the bone backwards towards the tail. Do this slowly to avoid pulling fish with the bone.

6. Discard the bone and feel over the fish for any other bones. Pin-bone it, using kitchen tweezers, and trim the belly area to neaten the fish. It is now ready to cook.


If you don’t want to serve the fish with the head on, cut it off before gutting the fish, which will make it easier to gut and to open and flatten the fillets against the board before releasing the bone with your thumb.

Smoked fish

Smoking is a technique traditionally used to preserve fish, but is now often used to flavour and add texture rather than to preserve.

Fish can be cold- or hot-smoked. Cold smoking is where the fish is smoked over cool smoke so the fish is not actually cooked and may require further cooking. Examples of cold smoked fish include traditional smoked salmon, eaten just cold-smoked, and smoked haddock, which requires further cooking.

Hot-smoked fish is smoked over hot smoke so the fish cooks as it takes on a smoky flavour. Fish smoked this way needs no further cooking and can be eaten straight away. Examples include kippers (hot-smoked herring), eel, and hot-smoked salmon and trout.

Cured fish

This is another method of preserving fish, by drawing out some of the liquid either with a dry cure, as in gravadlax, or an acidic marinade that ‘cooks’ the flesh as it starts to pickle and preserve it, as in ceviche. Herbs and aromatics can be used to impart flavour during the process.

Featured Recipes in this Chapter

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