Pumpkin Soup

Peel the pumpkin with a sturdy peeler or a sharp knife, scrape out the seeds and stringy fibres with a spoon and cut the flesh into 3 cm chunks. You should have about 1.1 kg.

Trim the leek, keeping only the white and pale green parts, halve it lengthways and slice it thinly. Rinse the slices in a colander under cold running water to wash out any grit, then drain well. Peel and finely chop the onion. Peel the potato and cut it into 2 cm chunks.

Set a large heavy-based pot, about 4 litres, over medium heat. If using the pumpkin seeds, toast them in the dry pot for 3 to 4 minutes, shaking it often, until they puff up, start to pop and turn golden in places, then tip them onto a plate.

Lower the heat to medium-low and melt the butter in the pot. Add the onion and leek with a pinch of salt, cover and let them sweat for 10 minutes, stirring now and then, until very soft and translucent but not coloured. Turn the heat down if they start to brown.

Add the pumpkin and potato and stir to coat them in the butter. Cover and cook for 5 minutes, stirring once or twice.

Pour in the stock, which should just cover the vegetables. Bring to the boil, then lower the heat, half-cover and simmer for 20 to 25 minutes, until the pumpkin and potato crush easily against the side of the pot with a spoon.

Take the pot off the heat and blend until completely smooth and velvety, about 2 minutes with a stick blender. In a jug blender, work in batches, fill it no more than half full and hold the lid down with a folded tea towel, as steam can push it off, then pour the soup back into the pot.

Stir in 150 g of the crème fraîche and the nutmeg and reheat gently without letting the soup boil. Season with salt and black pepper. If it is thicker than you like, loosen it with a splash of hot water: it should coat the back of a spoon and pour slowly from the ladle.

Finely snip the chives. Ladle the soup into warm bowls, swirl a teaspoonful of the remaining crème fraîche into each and scatter over the chives and the toasted pumpkin seeds, if using.