1. Combine all of the ingredients listed under filling and refrigerate until ready to assemble pierogi.
2. Combine flour, salt and butter in food processor.
3. In a separate bowl, blend together egg, egg yolk, milk and sour cream.
4. Add egg mixture to flour mixture and process until dough cleans sides
of bowl and sticks together (the dough will be slightly sticky).
5. Remove from processor, shape into a ball, wrap in plastic and chill for 3 hours or overnight.
6. Cut dough into thirds; roll each section out on floured surface into 12" round.
7. Cut each round into 8 (3") circles (using a glass works well).
8. Place about 2 tsp filling on each dough circle.
9. Moisten outer edges with water and fold dough over to close.
10. Seal edges by pressing gently with the back of a fork or pinching together with your fingers.
11. In large pot, bring salted water to boil.
12. Cook 12 pierogi at a time, reducing heat to a gentle boil; boil until pierogi float to the surface (about 5 minutes).
13. Remove with a slotted spoon, drain on paper towel and transfer to serving dish.
14. Repeat with remaining pierogi.
15. At this point you can serve them warm, freeze them for later use or fry
them in butter over medium heat, lightly browning both sides before
serving.
