Clean, wash and roughly dice the soup greens. Boil up the soup greens, peppercorns, bay leaves and meat in approx. 1 1/2 litres of water. Leave to stand for approx. 2 hours at low heat. Clean, wash and slice carrots and celery.
Peel and wash the potatoes. Take out meat, pour stock through a sieve, remove 1/4 litre of it. Bring the rest of the stock, meat and fresh vegetables to the boil again and let it simmer for 20 minutes at low heat.
Heat the fat in a pot and sauté the flour in it. Deglaze with 1/4 litre stock and milk and boil thoroughly while stirring. Season to taste with salt, pepper and horseradish. Wash the herbs, chop finely and add.
Cut the meat open and arrange it covered with the vegetables and some sauce. Remaining sauce extra is enough.