Potato-Filled Vareniki or Pierogi

• 6 tablespoons (3/4 stick) butter, more or less
• 2 large onions, diced
• Salt and black pepper to taste
• 1 teaspoon minced garlic, optional
• 2 cups well-seasoned mashed potatoes
• 1 recipe Wrappers for Vareniki, Pelmeni, or Pierogi (page 58)
• 2 egg whites, lightly beaten
• Sour cream for garnish

1. Put 2 tablespoons of the butter in a skillet over medium heat and add the onions, along with a liberal sprinkling of salt and pepper.
2. Cook, stirring occasionally, until the onion wilts, then turns brown, as long as 30 minutes.
3. Its okay if the onion gets a bit crisp on the edges, but dont cook it too fast; basically you want a kind of onion compote.
4. Combine half the onions and the garlic, if youre using it, with the mashed potatoes, then taste and adjust the seasoning.
5. Lay a wrapper on a work surface, then place 1 to 2 teaspoons of the filling in the center of it; brush the edges of the wrapper with egg white, then pinch tightly to close.
6. If you have cut circles, form half-moons; if you have cut squares, form triangles.
7. Press the seam tightly to seal; its best if no air is trapped between the filling and wrapper.
8. Set on a lightly floured plate or wax paper.
9. (At this point, you may cover tightly and refrigerate for up to a day or freeze for a couple of weeks.)
10. To boil the dumplings, melt the remaining butter, set a large pot of water to boil, and preheat the oven to 200F.
11. Salt the water and boil the dumplings a few at a time until they rise to the surface.
12. A minute or two later, taste a bit of the dough to see whether it is tender.
13. As they finish, remove the dumplings with a slotted spoon and put them in an ovenproof bowl; drizzle them with some of the butter and put the bowl in the oven.
14. When the dumplings are done, make sure they are coated evenly with butter.
15. Reheat the reserved onions and toss them with the pierogi.
16. Serve hot with sour cream.
17. Put about 2 tablespoons butter in a large skillet, preferably nonstick, over medium heat.
18. When the butter melts, add as many dumplings as will fit without crowding and brown them quickly, turning once or twice.
19. Keep warm on a plate in the oven, cooking the remaining dumplings and adding butter to the skillet as needed.
20. Serve hot.
21. Use Kasha with Bacon and Onions (page 529) or Kasha with Mushrooms (page 529) as a filling.

butter, onions, salt, garlic, potatoes, recipe wrappers, egg whites, sour cream

Taken from www.epicurious.com/recipes/food/views/potato-filled-vareniki-or-pierogi-385630 (may not work)