Peel, wash and halve the kohlrabi. Cover and cook in about 3/4 l boiling salted water for about 20 minutes. Lift out and let cool down a little. Measure out 1/2 l stock. Hollow out the kohlrabi and put the inside aside
Cover the rice and cook it in about 400 ml boiling salted water at low heat for about 20 minutes
Peel and chop the onions. Fry onion and kohlrabi inside in hot fat. Deglaze with stock and cream. Let it boil down for about 5 minutes. Wash the chervil, add to the sauce and puree finely. Stir in half the cheese
Fill the kohlrabi with rice. Place in a greased casserole dish. Sprinkle with rest of cheese. Spread the sauce around it. Bake in a hot oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for about 30 minutes
Wash the tomato, cut into quarters, remove seeds if necessary, dice finely. Spread over the kohlrabi