Cut the kohlrabi and carrots into slices. Sweat the finely chopped onions in hot fat and add the vegetables, sauté and season for about 10 minutes.
Layer everything in a greased baking dish. Whisk the creme fraîche, cream, eggs and grated cheese. Season to taste and pour over the vegetables. Bake in a preheated oven at 200 ° C for approx. 50 minutes.