Peel onions and cut them into rings. Heat 3 tablespoons of oil. Fry the onions for about 10 minutes. Bring the stock to the boil. Cook vegetables for 5-7 minutes. Bring 1/2 litre water and a level teaspoon of salt to the boil in a saucepan.
Remove the pot from the heat and add the milk. Stir in the purée flakes briefly. Stir again after 1 minute. Drain the vegetables. Remove onions from the pan. Add the remaining oil to the frying fat and heat up. Fry the meatloaf for 2-3 minutes on each side. Add onions and heat briefly. Keep Leberkäse and onions warm. Heat 30 g fat in the frying fat. Swivel the vegetables in it and take them out. Heat up the remaining fat.
Add onions and heat briefly. Keep Leberkäse and onions warm. Heat 30 g fat in the frying fat. Swivel the vegetables in it and take them out. Heat up the remaining fat. Arrange Leberkäse with onions, vegetables and mashed potatoes on plates. Pour liquid fat over the mashed potatoes. Garnish with parsley as desired