Knead 2 eggs with enough of the flour to make a very, very hard dough.
Grate the dough. (So far the dough is like egg barley.)
Bring milk to a boil and simmer grated noodles in it over low heat, stirring. Cook until the milk is absorbed. Add more milk if necessary. Add alittle salt and pepper and mix in the chopped parsley. Cool to lukewarm temperature.
Mix cooled noodles with 3 egg yolks, then fold in the stiffly beaten whites of 3 eggs.
Grease a heavy casserole, 3- or 4-quart size, 3 to 4inches deep, with 1tablespoon lard. Pour the noodle and egg mixture into it and pat it down evenly.
Cook calf’s lung for 30 minutes. Drain, and put it through the meat grinder.
Sauté the onion in remaining 1tablespoon lard for about 10 minutes. Mix onion with ground lung. Add apiece of pepper and salt to taste. Let cool.
When lukewarm, mix in remaining 2 whole eggs, beaten.
Make a hole in the middle of the cooked noodle mixture in the casserole, and pour in the lung mixture. Spread the entire top with sour cream. Bake in a 375°F. oven for 45 minutes.