Peel the onion and cut into cubes. Wash, peel and slice the carrots and celery (it is best to quarter the celery beforehand). Wash the leek and cut into rings.
Let the butter get hot in a saucepan and sauté the vegetables in it. Add 1/4 liter of water and bring to the boil. Dissolve the vegetable stock in it and cook for approx. 20 minutes.
Take out some vegetables with a slotted ladle and set aside. Puree the rest of the vegetables.
Add the rest of the water and cook for approx. 5 minutes.
Season with pepper and ginger powder and season to taste. Then add the vegetables that have been set aside.
Arrange the soup in plates and garnish with the crème fraîche and chives.