Clean and peel the potatoes, cut them into quarters, and place them in a pot with just enough water to cover them

Cover the pot and boil the potatoes for 20 to 40 minutes, until tender

Drain them as soon as they are done

While the potatoes are cooking make a full load of pierogi dough using the above ingredients

Make pierogi shapes according to the instructions for halfmoon ravioli in the Making Pasta chapter

Sheets of pasta dough should be about 1/8 inch thick, cut into 2 or 3-inch circles

Mash the potatoes while they are still warm

Fry the onion in the butter

Combine the potatoes, onion, and cheese in a bowl and mix well, adding salt and pepper to taste

Drop about 1 tablespoon of filling onto the center of each round

Moisten the exposed dough with water and fold each circle in half

Seal the open edges of the semicircle by pressing them together

Boil the pierogi for 5 to 8 minutes in salted water

Drain and serve them with melted butter and sour cream.