Cut the rolls into small cubes and place them in a bowl. Peel and finely dice the onion. Heat the fat and fry the onion until transparent. Heat the milk and mix it with the onion into the rolls.
Cover and leave to stand for 20-30 minutes.
Wash the parsley, shake dry and chop the leaves finely, except for a little to garnish. Add the egg and parsley to the rolls, knead the mixture well with your hands, season with salt and pepper.
Bring a large saucepan with plenty of salted water to the boil. Wash the red cabbage leaves and cook for about 5 minutes. Remove and rinse in cold water. Fill the leaves with the bread roll mixture and fold into small packets.
Tie up with kitchen string. Place in the hot salted water and leave to stand for about 15 minutes. Drain finished parcels and arrange on a plate. Garnish with parsley.