Clean, wash and chop the leek. Peel, wash and dice parsley root, carrots, celery and potatoes. Heat the oil in a large pot and sauté the vegetables in it. Deglaze with 1.5 litres of water, cook over medium heat for about 20 minutes
Wash the chives, dab dry and cut into rings. Cut marjoram finely and mix with sour cream. Season to taste with salt, pepper and sugar. Season soup with salt, pepper, 1 pinch of sugar and nutmeg. Serve the soup, sprinkle with chives. Serve with baguette bread (ask the baker for lactose-free variety)