Cut the pumpkin flesh into small cubes. Peel the onions and finely chop them together with the parsley.
Melt the margarine. Sweat the chopped onion in it, then add the pumpkin cubes and fry for about 2 minutes. Dust the flour over the pumpkin pieces and sauté briefly. Pour in the chicken stock, bring to the boil and cook everything over low heat for about 10 minutes. Vigorously stir (or puree) the soup and season with salt, pepper and nutmeg. Fold in the sour cream. Sprinkle with parsley on top.