Soak the livers in milk, then drain them. Stew the sliced onion until soft in some of the butter. Add the chopped livers, which you've rolled in flour and mix well. Cut the peppers into thin strips, grate the tomatoes on a grater.
Sauté the peppers, tomatoes and paprika in the remaining butter. Add them to the livers and pour some hot water over them. Season with salt and pepper and sauté on low heat until the vegetables are left in just butter.
Sprinkle with parsley and serve.