Boil the meat whole and cut into portions. Peel potatoes and cook whole in the same broth.
Roll out the dough for noodles thinly, cut into diamonds, boil in salted water until soft, remove and brush with butter.
Put noodles, meat and potatoes in a deep plate, put thinly sliced onion on top, sprinkle with chopped parsley. Serve hot broth and mustard separately.