30g butter
1kg floury potatoes
400ml double cream
2 large garlic cloves, crushed
¼ teaspoon freshly grated nutmeg
Sea salt and freshly ground black pepper

Preheat the oven to 160°C/Gas Mark 3. Rub a gratin dish liberally with the butter.

Peel the potatoes and slice them thinly, either with a sharp knife or a mandoline. In a large bowl, whisk together the cream, garlic and nutmeg and season well with salt and pepper. Toss the potatoes in the creamy mixture, then layer them in the gratin dish, spreading them as flat and evenly as you can. Pour over any remaining cream.

Bake for 1 –1 hours, pressing down with a spatula every 15 minutes or so to compress the potatoes and stop them drying out. The gratin is ready when the top is golden and bubbling and the potatoes are tender. You may want to turn the oven up to 190–200°C (Gas Mark 5 or 6) for the last 5 minutes to achieve a bit of extra bubbling crispness.

Leave to stand for 5 minutes or so before serving.

For something a little more virtuous, you can substitute half the cream for whole milk. That goes for the following variations too.