Peel, wash and slice the potatoes. Clean the kohlrabi, setting aside 2 kohlrabi leaves, peel and cut into bite-sized pieces. Cook the vegetables in boiling salted water for about 8 minutes and drain.
Catch the vegetable stock. Wash the meat and dab dry. Fry on each side in hot oil until golden brown. Season with salt and pepper. Fry over medium heat for about 10 minutes, set aside.
Heat the fat in the frying oil. Sweat flour in it. Add 1/4 litre vegetable stock and cream while stirring constantly and bring to the boil. Grate cheese. Melt half in the sauce. Season to taste with salt, pepper and nutmeg.
Cut the fillets open. Fill vegetables and fillet into an ovenproof dish. Pour sauce over them. Wash the kohlrabi leaves, cut into fine strips and sprinkle over the top. Sprinkle the rest of the cheese on top as well.
Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for approx. 20 minutes. Serve sprinkled with dill as desired.