Step 1

Preheat the oven or toaster oven to 350 degrees F.

Step 2

For the filling: Into a large mixing bowl, add the mashed potato and two-thirds of the crumbled bacon, reserving the remaining bacon for topping.

Step 3

In a large nonstick or cast-iron pan over medium heat, add a thin layer of the reserved bacon fat. Add the onions and cook until lightly browned, 10 to 12 minutes. Remove the onions from the pan and add half into the bowl with the potato and bacon, reserving the remaining onions for topping. Add the ricotta, chives, salt and pepper. Mix to thoroughly combine. Cover and refrigerate until you’re ready to make the pierogi. Keep the pan handy, as you’ll use it again.

Step 4

For the dough: In a large mixing bowl, whisk together the flour and salt. In another bowl or measuring cup, whisk together the warm water, yogurt and egg. Make a well in the center of the flour and pour in the wet mixture, then mix with a wooden spoon or with your hands to form a shaggy dough. Turn out onto a floured surface and knead for a few minutes until you have a smooth and soft dough that is slightly sticky. Wrap and refrigerate for 1 hour.

Step 5

Prepare a baking sheet with a generous dusting of flour. Remove the potato filling from the refrigerator.

Step 6

To assemble the pierogi: Dust a clean work surface with flour. Working with a quarter of the dough at a time, roll out the dough to 1/8 inch thickness. With a 3-inch round cookie cutter, cut as many circles as you can (about 6 per quarter of dough after the first roll. The dough can be rerolled once to yield another 2, for 32 total.). Put a heaping tablespoon of filling in the center of each circle of dough, then pinch the edges to seal and pleat the seam. Once sealed, fold the edge over itself to crimp from one end to the other, pinching as you go. Place on the floured baking sheet while you assemble them all. At this point, you can cook the pierogi immediately or freeze them for up to 2 months.

Step 7

To cook the pierogi: Bring a large pot of salted water to a boil. Drop in several pierogi at a time and cook until the pierogi float, about 3 minutes.

Step 8

Heat the skillet over medium heat. Add enough reserved bacon fat to coat the bottom of the pan. Use a spider to drain the boiled pierogi as much as possible, then add them to the hot bacon fat and fry, in batches, for 2 to 3 minutes undisturbed on each side, or until lightly golden, adding more bacon fat, or neutral oil, if the pan gets too dry.

Step 9

Remove the fried pierogi to a serving platter or large, shallow serving bowl. Add the remaining half of the cooked onions and bacon to the pan and cook to reheat, 1 to 2 minutes. Transfer to the serving bowl. Top the pierogi with sour cream, chives, black pepper and flaky salt if desired.