Chop the potatoes into walnut-sized chunks and tip into a large pan of cold, salted water. Bring to the boil, then reduce the heat and simmer gently for 10 mins, or until the potatoes are cooked through and fluffy at the edges but still holding together. Drain. (Or, cook in the microwave – see tip, below.) The potatoes can be boiled the day before and chilled.

Heat the oven to 210C/190C fan/gas 6 1/2. Pour the oil into a large roasting tin so it covers the base – there should be a depth of about 1/2cm. Put the tin in the oven for 5 mins to heat up, then remove from the oven. Carefully tip the drained potatoes into the hot oil, and use a spatula to turn them to coat. Roast for 40 mins, then remove from the oven and turn the potatoes over using the spatula. Roast for 20 mins more, then repeat this process again for a final 20 mins until the potatoes are deeply golden and crunchy. (Or, cook in an air fryer – see tip, below.) Season to serve.