Peel, wash and chop the potatoes and carrots. Clean and wash the leek. Separate the white and green from the leek and cut into thin rings. Peel ginger and chop finely.
Briefly fry the leek in 1 tbsp. hot oil. Season with salt and pepper and remove. Steam potatoes, carrots and the rest of the leek in 1 tablespoon of oil for about 4 minutes. Fry ginger briefly. Season with salt, pepper and 1 pinch of sugar.
Pour on 1 l water, add stock and bring to the boil. Cover and simmer for about 20 minutes.
Wash the coriander and chop finely, except for a little bit. Puree the soup, season to taste, refine with crème fraîche and coriander. Garnish with leek green and the rest of the coriander. Serve with bread and butter.