Slice potatoes into pieces and boil in salted water until done, drain the water and mash potatoes into a puree. Let it cool, add the egg, salt, nutmeg and potato flour. Using wet hands, shape the potato mixture into balls (about 7). Boil the salted water in a big saucepan, roll dumplings in flour and place into a saucepan( the water shouldn't boiling). Crumble the stale bun and fry in a half of the butter until golden brown. Mix another half with chopped parsley. Serve dumplings with bread crumbs and parsley.