Peel onions, cut them into rings and turn them slightly in flour. Quarter Leberkäse. Put the vegetables in a pot with 250 ml water without defrosting. Cook for about 10 minutes at low heat. Season with salt and pepper if necessary.
For the puree, boil 1/2 litre of water and 1 teaspoon of salt. Remove the pot from the heat and add milk. Stir in the puree flakes. Stir again after 1 minute. Fry meatloaf in 1 tablespoon of hot oil for 1-2 minutes on each side, remove.
Add the remaining oil to the frying fat. Fry the onion rings for about 2 minutes over high heat while turning. Arrange vegetables, mashed potatoes and meat loaf on plates. Add the onion rings. Serve sprinkled with parsley and garnished.