Peel, wash and cut the kohlrabi into sticks. Cook in boiling salted water for about 10 minutes. Wash the fish, dab dry and sprinkle with lemon juice. Season with salt and pepper and turn in flour. Fry in 40 g hot fat on both sides for 3-5 minutes. Drain the kohlrabi and collect the cooking water. Measure 1/4 litre and heat up, stir in sauce powder and bring to the boil.
Dice remaining butter and stir into the sauce bit by bit. Do not boil any more. Wash and chop the tomatoes. Pluck the coriander leaves from the stalks. Add the kohlrabi, tomatoes and coriander to the sauce and warm it up. Arrange fish and vegetables on plates. Serve with rice or boiled potatoes