Clean and wash the kohlrabi, put 1/2 kohlrabi aside. Chop the rest of the kohlrabi roughly. Peel onion and chop finely. Peel potatoes, wash thoroughly and dice coarsely. Heat oil in a pot, fry onion until translucent, add diced kohlrabi and potatoes, fry briefly.
Add chervil. Deglaze with broth, bring to the boil, cover and cook for about 20 minutes. Meanwhile cut half the kohlrabi into slices, put into boiling salted water and cook for about 12 minutes. Wash, clean, quarter, seed and finely dice the tomato. Remove the kohlrabi potato vegetables from the stove and puree them in the broth with the hand mixer's hand blender. Add cream, stir in, bring to the boil again. Season to taste with salt, pepper and sugar. Pour kohlrabi slices into a sieve, drain and add to the soup. Serve in deep plates sprinkled with tomatoes and garnished with chervil.
Remove the kohlrabi potato vegetables from the stove and puree them in the broth with the hand mixer's hand blender. Add cream, stir in, bring to the boil again. Season to taste with salt, pepper and sugar. Pour kohlrabi slices into a sieve, drain and add to the soup. Serve in deep plates sprinkled with tomatoes and garnished with chervil. Roasted thin baguette slices taste good with it