Peel the potatoes and wash them thoroughly. Cook in boiling salted water for about 25 minutes. In the meantime peel onions and cut them into fine rings. Wash the liver and pat dry. Wash apples, quarter them and cut them into slices.
Dust onion rings with 2 tbsp. flour, tap lightly. Turn liver in 4 tbsp. flour, tap lightly. Heat 2 tbsp. butter in a large pan. Fry the liver for 2-3 minutes on each side. Season with salt and pepper, remove from the pan and keep warm.
Heat 2-3 tablespoons of butter in the frying fat. Fry apples and onions for about 4 minutes, turning them over. In the meantime heat milk and 3 tbsp. butter. Drain potatoes, add milk-butter mixture and mash with a potato masher.
Season to taste with salt and nutmeg. Arrange liver and mashed potatoes on plates. Spread apples and onions together with frying fat over the liver. Garnish with parsley.