2 cups sour cream
4-1/2 cups all purpose flour
2 Tbsp. melted butter
2 eggs plus 1 egg yolk
2 tsp. salt
2 Tbsp. vegetable oil

In a large bowl, mix all the ingredients and knead into a soft
pliable dough. Cut in half and let rest, covered for 10 minutes.
Roll out each half into a thin circle. Using a drinking glass,
cut the dough into round circles and fill them with cheese or
other filling. Place less than a tablespoon of filling in the
center of each circle and fold over. Press and seal into a half
moon. You may want to rub a little water on the edge to seal
well. Cook for 10 minutes in boiling salted water. Drain. Then
pan fry in butter.

Cheese Pierogi Filling (my favorite)

1 cup dry curd cottage cheese or farmer's cheese
2 tsp butter, melted
1 egg beaten
2 Tbsp. sugar
1 Tbsp. lemon juice

Run the cheese through a ricer or a coarse sieve. Then mix well
with remaining ingredients.