Slice hard rolls thinly and place in a large bowl; set aside to dry overnight.
Bring large kettle of salted water to boil. Soak bread in warm milk. Bread should be moist, but not soggy. Fry onion and bacon in butter until onion is tender. Stir onion and bacon into moist bread. Add parsley flakes, eggs, salt and pepper to bread. Stir to combine all ingredients. Shape into large dumplings. Drop into boiling water. Simmer uncovered, for 20 minutes, or until dumplings rise to surface.