Clean and peel the kohlrabi and chop the beautiful leafy greens into small pieces. Halve the peeled kohlrabi and cut into thin slices. Bring salted water to the boil and cook the kohlrabi until soft. Steam the onion cubes in hot, foaming butter until they are translucent. Dust with the flour and create a light-colored burn. Deglaze with the milk. Drain the kohlrabi in a sieve and collect the vegetable stock. Fill the roux with it until a creamy sauce is obtained. Add the chopped leaf greens along with the spices. Finally insert the kohlrabi slices.