Polish pierogi

1. Doughi: mix flour, eggs, sour cream, salt, and water, a little at a time.
2. Kneadi dough until firm and elastic; cover and let rest 10 minutes.
3. Potatoi filling: prepare potatoes, set aside.
4. Cheesei flling: combine ingredients and mix. Saucei: saute onion in butter until golden.
5. Assembly: divide dough into three parts.
6. On a floured surface roll dough to about 1/8-inch thick; cut into 3-inch rounds.
7. Place a small spoonful of the filling in the center of each round, fold and press the edges together firmly to seal.
8. Drop the pierogi in simmering chicken bouillon with 1 teaspoon of oil. Do not crowd.
9. Simmeri for 15 minutes, stirring gently to prevent sticking.
10. Remove with a slotted spoon and drain well.
11. Place the drained pierogi in a casserole and pour sauce mixture over all. Garnishi with mushrooms.