Cheese and Potato Pierogi

Make the dough: combine 2 cups all-purpose flour, 1/2 tsp salt (for dough), 1 large egg, 1/2 cup sour cream (for dough), and 3 tbsp warm water in a bowl. Mix until a shaggy dough forms, then knead on a lightly floured surface for 3 to 4 minutes until smooth and elastic. Wrap in plastic and rest for 30 minutes.

Make the filling: boil 1 lb peeled, cubed russet potatoes in salted water for 15 minutes until very tender. Drain and mash until smooth. Stir in 1 cup shredded sharp cheddar cheese, 3 tbsp softened cream cheese, 1/2 tsp salt (for filling), and 1/4 tsp black pepper. Let cool completely.

Caramelize the onion: melt half the 4 tbsp unsalted butter in a skillet over medium-low heat. Add 2 thinly sliced yellow onion and cook, stirring occasionally, for 20 to 25 minutes until deeply golden. Set aside.

Roll the dough out on a floured surface to about 1/8-inch thickness. Cut into 3-inch rounds using a glass or cutter.

Place a heaping teaspoon of filling in the center of each round. Fold the dough over to form a half-moon and press the edges firmly to seal, crimping with a fork or your fingers.

Bring a large pot of salted water to a boil. Cook the pierogi in batches for 3 to 4 minutes after they float to the surface. Remove with a slotted spoon.

Melt the remaining unsalted butter in a large skillet over medium-high heat. Add the boiled pierogi in a single layer and pan-fry for 2 to 3 minutes per side until golden and crispy.

Serve hot topped with the caramelized onion and a dollop of 1/2 cup sour cream (for serving).