Brown onions in butter. Dissolve bouillon cubes in boiling water. Add flour to onions. Add bouillon cubes to onions; set aside and let completely cool. Drain sauerkraut well; grind sauerkraut and meat together. Add to onion mixture and stir well. Form into balls.
Beat eggs with milk. Roll balls in flour, then dip in milk, egg mixture, then roll in bread crumbs and deep fry in hot oil. May freeze and reheat in oven at 350 degrees for 15 to 20 minutes.