You can serve it hot or chilled. Normally, I would serve this with bread – but not for Christmas dinner, as you want to stimulate your guests’ appetites.

Serves 6

1.5kg leeks
3 cloves garlic, roughly chopped
8 stems lemon grass, finely sliced
5 tbsp extra-virgin olive oil
2 large potatoes, peeled and diced
400ml crème fraîche
3 tbsp finely sliced chives

Trim the leeks, discarding the outer leaves and dark-green tops. Cut in half lengthwise and wash thoroughly. Finely slice, then put in a colander. Rinse again and leave to drain.

Gently fry the garlic and lemon grass in the olive oil in a large pan for 4 minutes. Mix in the potatoes and continue to fry over a low heat, stirring regularly until they begin to soften – about 8 minutes. Stir in the leeks and continue to fry for about 7 minutes or until soft.

Add 1.5 litres of water and season to taste. Bring to the boil, then simmer over a moderate heat for 25 minutes or until very soft. Liquidise until smooth, then pass the mixture through a sieve. Stir in 300ml of the crème fraîche and adjust the seasoning to taste.

Reheat to serve. Beat the remaining crème fraîche with a fork to thin it slightly, then ladle the hot soup into bowls, add a generous swirl of crème fraîche and sprinkle with chives. Serve immediately.

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