Polish Pierogi with Potato and Cheese Filling, Served with Caramelized Onions

For the dough, combine 3 cups all-purpose flour and 1 teaspoon salt in a large bowl. In a separate bowl, whisk 1 large egg with 1 cup warm water. Gradually add the wet ingredients to the dry, mixing until a shaggy dough forms. Turn onto a lightly floured surface and knead for 5-7 minutes until smooth and elastic. Cover with a clean kitchen towel and let rest for 30 minutes.

For the filling, peel and cut 2 pounds Russet potatoes into 1-inch cubes. Boil in salted water for 15-20 minutes until very tender. Drain well and mash thoroughly. Add 1 cup farmer's cheese, 1/2 teaspoon black pepper, and salt to taste. Mix until well combined and smooth. Set aside to cool completely.

While the dough rests and filling cools, prepare the caramelized onions. Slice 2 large yellow onions thinly. Melt 2 tablespoons unsalted butter in a large skillet over medium-low heat. Add the sliced onions and cook for 25-30 minutes, stirring occasionally, until deeply golden brown and very soft.

Divide the rested dough into two portions. On a lightly floured surface, roll out one portion to about 1/8-inch thickness. Use a 3-inch round cookie cutter or glass rim to cut out circles. Place about 1 teaspoon of the potato and cheese filling in the center of each circle. Fold the dough over and pinch the edges firmly to seal, creating a half-moon shape.

Bring a large pot of salted water to a rolling boil. Carefully drop the pierogi into the boiling water, working in batches to avoid overcrowding. Cook for 2-3 minutes after they float to the surface, ensuring the dough is cooked through. Remove with a slotted spoon and drain well.

In a separate large skillet, melt the remaining 2 tablespoons unsalted butter over medium heat. Add the boiled pierogi in a single layer and pan-fry for 2-3 minutes per side, until golden brown and slightly crispy. Repeat with remaining pierogi.

Serve the pan-fried pierogi immediately, topped generously with the caramelized onions.