Pierogi (Potato & Cheese)

2 eggs whisk
wet
knead & rest
dough
roll & cut
dough
fill & seal
pierogi
boil, then fry
with onion
2 Tbs. sour cream
1 cup milk
3 1/2 cups flour
2 tsp. salt
3 lb large potatoes boil & mash
potatoes
potato-cheese
filling
1/4 cup warm milk
4 Tbs. unsalted butter
1/2 cup cheddar cheese
1 large onion
2 Tbs. unsalted butter, to fry