Boil the potatoes and mash them well with a fork. Grate the washed onions, feta cheese and cheese, chop the parsley finely and the bacon into small cubes.
In a deep container, mix all of the ingredients with the egg whites, black pepper and salt to taste. Knead everything well until the flavors mix into one.
Form meatballs from the mixture and beat the yolks with a fork. Roll each meatball first in breadcrumbs, then in the egg whites.
Fry them in highly heated oil until golden. Put the meatballs on paper towels to drain away the excess oil.