Hasselback Potatoes

Preheat the oven to 200°C (Gas Mark 6). Wash the potatoes, then carefully make a series of slices across the width of each one; you need to slice about three-quarters of the way down to the bottom of the potato, and the slices should be about 4mm apart. It helps to put a wooden spoon flat on the work surface and sit the potato in the bowl of the spoon, so that it remains steady as you slice.
Mix together the melted butter and oil and pour it into a roasting tray. Put the potatoes into the tray and spoon the fat over them, making sure that each potato is well coated. Grind over some black pepper, sprinkle over the salt flakes and then put into the hot oven. Roast the potatoes for about 45 minutes, until they have fanned out beautifully and become golden and crispy, then serve.