Clean, wash, quarter and cut the peppers crosswise into strips. Clean and wash spring onions and cut them into three centimetre long pieces. Fry the bell peppers and spring onions one after the other in 20 grams of fat, season with salt and pepper.
Cut the sausage into strips. Cut white bread into cubes. Boil up the remaining fat with milk and pour over the bread cubes. Wash and peel potatoes, grate coarsely and mix with egg and sour cream.
Season with salt, pepper and nutmeg. Grease a flat casserole dish of 2.5 litres. Layer potato mixture, paprika, mettwurst, spring onions and bread cubes one after the other. Sprinkle with grated cheese.
Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for 40 to 45 minutes. Chop parsley, except for a few leaves. Garnish crust cake with parsley.