Cut the pumpkin into pieces.

Peel each piece, then remove the stringy fibers and the seeds.

Peel the potatoes.

Cut the potatoes into pieces.

Rinse the pumpkin and potato pieces, then set them aside.

Peel the onion.

Chop it roughly.

Heat the olive oil in a large saucepan over medium-low heat.

Sauté the onion in the oil, stirring, without letting it brown, until it is translucent.

Add the pumpkin and potato pieces.

Pour in just enough water to cover the vegetables.

Season with salt.

Cover the saucepan and cook over medium heat for about 15 to 20 minutes, until the vegetables are tender: the pumpkin flesh should mash easily with a fork.

Turn off the heat.

Drain the vegetables in a colander set over a large bowl, to save the cooking water.

Add the crème fraîche to the drained vegetables.

Blend everything in a blender or with an immersion blender, adding the cooking water little by little until you have a smooth, creamy soup, as thick or as thin as you like.

Season with pepper.

Grate the nutmeg directly into the soup, then stir.

Toast the pumpkin seeds in a small dry frying pan over medium heat for 2 to 3 minutes, stirring, until they begin to turn golden and crackle.

Pour the soup into the bowls.

Place a spoonful of crème fraîche in the center of each bowl and swirl it into a spiral with the tip of a spoon.

Sprinkle with the toasted pumpkin seeds.

Serve immediately.