1. Heat oven to 200C. Rub cut garlic around base and sides of a shallow one-litre gratin dish, then lightly grease with butter. Peel and finely slice potatoes.

2. Gently heat cream, milk, nutmeg and garlic halves in a saucepan until just under the boil. Add potatoes to hot milk mixture and simmer for 10 minutes, jiggling them every now and then to stop them sticking.

3. Use a slotted spoon to layer half the potatoes in the gratin dish, scatter with half the cheese, salt and pepper, then top with remaining potatoes.

4. Discard garlic and pour hot milk over the top. Scatter with remaining cheese, sea salt and pepper and bake, uncovered, for 30 to 40 minutes, until potatoes are cooked and gratin is bubbling and richly golden. If not, raise heat to 220C for another 10 minutes before serving.

Tip Nigella Lawson says: "This is not the most labour-saving way of cooking potatoes, to be sure, but one of the most seductive. And it reheats well as an accompaniment to cold roast pork, or indeed anything, in the days that follow."

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