Pierogi (Traditional Polish Dumplings)

Step 1
Prepare filling: Heat oil in a large skillet over medium heat. Cook and stir onions and mushrooms in hot oil until soft, about 15 minutes. Remove from heat and set aside.

Step 2
Pass potatoes and farmer's cheese separately through a food grinder or food processor; place both in a large bowl. Add onion-mushroom mixture, sour cream, salt, and pepper; mix until well combined and set filling aside.

Step 3
Make dough: Place flour on a clean work surface and form a well in the center. Crack eggs into the well. Add butter and a few tablespoons warm water. Mix with your hands, gradually adding more warm water, 1 tablespoon at a time, as you go. Knead until dough is soft and smooth, adding more flour to the work surface as needed.

Step 4
Roll out 1/4 of the dough to an 1/8-inch thickness. Use a glass or round cookie cutter to cut out circles, saving any excess dough for your next batch. Place 1 teaspoon filling in the center of each dough circle. Fold dough over into a half-moon shape and pinch edges together to seal. Cover pierogi with a clean dish towel and repeat with remaining dough and filling.

Step 5
Bring a large pot of salted water to a gentle boil. Cook pierogi in batches, about 20 at a time, in boiling water until they float to the surface, 10 to 15 minutes. Remove with a slotted spoon to a strainer to drain.