Remove the outer leaves of the cabbage head. Halve the cabbage head, remove the stalk and cut the cabbage into strips. Wash in cold water and drain. Peel onions and cut into large cubes. Heat oil in a pot. Fry the savoy cabbage and onions for about 5 minutes. Deglaze with vegetable stock and simmer for about 10 minutes.
Season to taste with salt, pepper and nutmeg. Add cream. Refine with 50 g crème fraîche. Puree with a blender. Cut smoked salmon into fine strips. Serve the soup and serve with the remaining crème fraîche and smoked salmon