Clean and quarter the mushrooms. Clean the leek and cut into rings. Heat the oil in a high pan, fry the mushrooms and leeks in it, remove and set aside.
Peel the kohlrabi and peel the carrot and cut into cubes. Chop the onion and fry in a pan with a little oil. Add the kohlrabi and carrot cubes. Add the vegetable stock and simmer for about 20 minutes.
Add the mushrooms and leek. Season to taste with pepper and garlic granules. Stir in the creme fraîche and, if necessary, thicken with a sauce thickener. At the end, check again whether the kohlrabi cubes are really soft enough, otherwise it can taste slightly wooden.