If you’re as much of a sucker for a voluptuous, creamy gratin as I am you won’t need much persuading to try this sweet potato version. It’s ludicrously rich, so a little goes a long way. But (psychologically at least), adding some chilli does temper the feeling that one’s arteries are narrowing perceptibly with each mouthful. The gratin looks rather jolly made with different-coloured potatoes. But don’t worry if you can get only a single variety. It will keep, made-up, for a couple of hours before being baked, but not much longer.

Shallots
Garlic gloves
1kg mixed orange and white-fleshed sweet potatoes
A (568ml) carton of double cream
Ground cumin
Chilli sauce
Butter

METHOD Finely chop two shallots and two garlic cloves. Peel the potatoes, then put them through the fine slicing blade of a food processor. Tip them into a very large bowl with the shallots and garlic. Add the cream, a teaspoon of ground cumin and a tablespoon of chilli sauce. Use your hands to mix all the ingredients together very thoroughly.

Preheat the oven to 140C fan/gas mark 3. Butter a 26cm-28cm ovenproof dish.

Put a layer of cream-coated potatoes in the bottom of the dish and add seasoning. Add another two layers, seasoning each time. For the final layer, carefully alternate the colours and arrange the slices in a neat concentric design. Pour any remaining cream over the top, dot with butter, then bake the gratin for about 90 min. Check to make sure that the cream isn’t bubbling because if the temperature is too high, the “sauce” will split. When the potatoes are tender to the point of a small knife, remove the dish and keep the gratin warm for 15 to 30 min. It actually tastes better warm rather than scalding hot.

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