Step 1

In a skillet over medium heat, melt butter and sauté onion 5 to 7 minutes or until tender. Remove 1/4 cup of onion and set aside. Continue to cook remaining onion 5 to 7 minutes or until golden; set aside. In a large saucepan, boil potatoes 15 to 20 minutes or until tender; drain and mash.

Step 2

In a large bowl, combine the 1/4 cup onion, the mashed potatoes, cheese, 1 teaspoon salt, and the pepper; mix well and set aside.

Step 3

To make the dough, in another large bowl, mix eggs and sour cream until smooth. In a medium bowl, combine 3 cups flour, the baking powder, and remaining 1/2 teaspoon salt; mix well. Add flour mixture to egg mixture and stir until dough comes together.

Step 4

Place dough on a lightly floured surface and knead until smooth. Divide dough in half and cover half with plastic wrap. Lightly flour your work surface and, with a rolling pin, roll out the dough to 1/8-inch thickness. Using a 3-inch cookie cutter or drinking glass, cut out the dough. Place 1 teaspoon potato filling in center of each dough round. Moisten edges with water, fold the dough over the filling and pinch edges together to seal. Repeat with remaining dough and potato mixture.

Step 5

Bring a large pot of salted water to a boil over high heat. Add pierogies in batches and cook 4 minutes. Remove with a slotted spoon to a paper towel-lined platter. Over medium heat, add pierogis to skillet with remaining onion. Cook until golden and heated through.