Clean, wash and cut the celery into pieces. Set aside some of the celery green from the inner leaves. Peel the onion and potato and cut into cubes.
Cook the celery, onions and potatoes in the vegetable stock for about 20 minutes. Then puree and fold in the crème fraîche. Heat again, but don`t let it boil anymore. Garnish the soup with washed celery leaves before serving.