Wash vegetables. Divide the cauliflower into florets. Peel the onions, carrots and kohlrabi. Cut the carrots and kohlrabi into bite-sized strips. Cook the carrots, kohlrabi, cauliflower in 200 ml water for 5 minutes until soft. Drain the vegetables, collecting the vegetable cooking water. Finely dice the onion. Heat the oil in a saucepan, add the onions and fry. Add the flour and sweat. Add the roux, vegetable cooking water and cream, stirring constantly. Add the spices and cook the sauce over a low heat for about 10 minutes, stirring repeatedly. Add the vegetables and cook briefly. Serve with low-protein noodles or potatoes.