Clean and wash the soup greens and tie them together with kitchen string. Boil 2 litres of water in a pot. Wash the meat and put it into boiling water together with the soup vegetables. Add salt, bay leaf and peppercorns and bring to the boil.
Cook the meat at low to medium heat for about 2-2 1/2 hours. In the meantime clean and wash the rest of the vegetables and cut them into long sticks. Cut parsley into fine strips, except for a little bit for garnishing.
For the semolina dumplings, boil 1/4 litre of milk, 60 g fat and a little salt. Remove from heat and stir in the semolina. Heat again while stirring until a dumpling is formed. Let it cool down a bit. Then stir in the eggs and half of the parsley.
Season with nutmeg. Remove meat and soup vegetables from the stock. Keep meat warm. Remove 1/4 litre of the stock for the sauce. Add prepared vegetables to the stock and cook for 8-10 minutes, drain vegetables.
Keep stock and serve as a pre-soup if necessary. In the meantime, boil up salted water in a pot. Use a tablespoon to cut off dumplings from the semolina mixture and let them simmer in the salted water for about 8 minutes.
For the sauce, heat the remaining fat in a saucepan and sauté the flour in it. Deglaze with reserved stock and remaining milk while stirring. Bring to the boil and boil for a few minutes. Add horseradish to the sauce and season with salt, pepper and lemon juice.
Cut the meat into slices and arrange on a plate with vegetables and dumplings. Garnish with parsley. Stir the rest of the chopped parsley into the horseradish sauce. Serve the sauce extra.