Halve the savoy cabbage, cut out the stalk. Cut the savoy cabbage into strips, wash and drain. Peel the onions and cut into large cubes.
Heat the oil in a large saucepan and sauté the onions until translucent. Add the savoy cabbage strips and sauté while turning. Season with salt, pepper and nutmeg. Deglaze with the vegetable stock and bring to the boil. Cover and simmer over medium heat for about 10 minutes.
Pour the cream into the soup and puree with a hand blender.
Refine with half of the creme fraiche.
Cut the smoked salmon into fine strips. Season the soup again with salt and pepper and serve in deep plates. Serve with creme fraiche and smoked salmon.