Soak rolls in cold water. Peel onions, dice two finely, cut one into rings. Squeeze out the buns well. Knead minced meat with half of the diced onions, bread roll, mustard and egg, season with salt and pepper. Shape into 8 meatballs
Clean, peel and cut the kohlrabi into pieces. Boil 500 ml water, stir in broth. Add kohlrabi, cover and cook for about 10 minutes. Wash, peel and chop the potatoes. Cook in boiling salted water for about 20 minutes
Heat the oil in a pan and fry the meatballs on each side for about 5 minutes. Drain the kohlrabi and collect the stock. Melt the fat in a pan and fry the remaining onion cubes. Sprinkle with flour and sweat while stirring. Measure 300 ml of the stock, add with milk while stirring. Simmer for 5 minutes
Wash the parsley, dab dry, put some aside for garnishing, cut the rest into fine strips. Drain the potatoes, let them evaporate briefly and sprinkle parsley over them. Add the kohlrabi and marjoram to the sauce and warm up. Season to taste with salt and pepper. Remove the meatballs and fry the onions in the cooking fat until golden brown. Arrange everything together, garnish with parsley