For the kohlrabi soup, peel and wash the kohlrabi and cut into thin strips. Peel and finely chop the onion and garlic clove and sauté in oil.
Add the kohlrabi and let it steam briefly before deglazing with soup and crème fraiche. Simmer over medium heat for about twenty to thirty minutes (depending on the thickness of the kohlrabi pieces).
Add the butter to the soup and puree in a blender or with a hand blender. Season to taste with salt, pepper and lemon juice, refine with whipped cream and add the sliced smoked salmon.
The leafy greens of the kohlrabi can also be used for kohlrabi soup!