Peel the pumpkin and remove the seeds. Cut the flesh into pieces. Peel and chop onion. Clean, wash and chop the leek. Put vegetables and broth in a pot. Wash marjoram, shake dry and, except for a few leaves for garnishing, add to the vegetables.
Season with salt and pepper. Cover and simmer for about 25 minutes at medium heat.
In the meantime, roast the nuts in a pan without fat until golden brown. Let them cool down on a flat plate. Finely puree the soup with the cutting stick. Season to taste with salt and pepper and nutmeg. Stir 2 tablespoons of crème fraîche into the soup and arrange in bowls.
Garnish with remaining crème fraîche, marjoram and nuts.