Classic potato bake

Method

1. Preheat the oven to 190°C and grease a large casserole dish, about 35 x 25 x 5 cm.
2. Wash the potatoes and cut them in half lengthways. Slice each half into 1 cm slices. Put the potato slices in a large saucepan with the salt and cover with cold water. Bring to the boil over high heat and boil until just tender, about 8–10 minutes, testing with the point of a sharp knife. Drain the potatoes, reserving about 250 ml of the cooking water, and return them to the saucepan over low heat for 2 minutes to ensure any excess water has evaporated. Transfer the potato slices to the casserole dish.
3. Meanwhile, melt the butter in a frying pan over medium heat and cook the bacon and spring onions, stirring occasionally, until the bacon is starting to turn golden and the spring onions are soft, about 10 minutes. Add the sour cream and stir until it starts to bubble, reducing the heat to medium–low if the sauce is catching on the bottom of the frying pan. Add 250 g of the cheese and the pepper and stir until the cheese has melted into the sauce. Stir in 125 ml of the potato cooking water until the sauce is smooth and the consistency of thick cream, adding more water as needed. Taste and add sea salt and more pepper if needed.
4. Pour the sauce over the potatoes. Using a large metal spoon, gently turn the potatoes until they are covered in sauce. Sprinkle the remaining cheese over the top of the potatoes and bake until bubbling and the cheese on top is melted and golden, about 30–40 minutes.
5. Allow to stand for 5 minutes before serving.