Slow-cooked beef fillet

Method

1. Preheat the oven to 80°C. Heat a frying pan over a medium heat until it is hot, then add a tablespoon of the oil. Place the beef in the pan and fry it briefly, turning it occasionally, until browned on all sides – no more than 2 minutes in total. Remove from the pan and allow to cool.
2. Lay out some clingfilm on a clean, dry work surface: you need 4 large rectangles that completely overlap. Place the beef along the long edge of the clingfilm and roll it up tightly, holding both ends so it forms a large cylindrical Christmas cracker shape. Tie a knot in each end and place in a roasting tin. Cook in the oven for 1 hour. Remove the beef from the oven and remove and discard the clingfilm.
3. Heat a frying pan until hot, then add the remaining oil and the butter. When it’s foaming, add the beef. Turn the fillet until evenly browned – no more than 30 seconds on each side. Remove the fillet from the pan, place it on a carving board and allow to rest for 5 minutes. Slice it thickly and season with salt and pepper, then serve with wholegrain mustard.