In a large bowl, mix the flour and salt. Create a well in the center and add the egg and water. Mix until a rough dough forms. Knead on a floured surface for about 5 minutes until smooth. Wrap in plastic wrap and let rest for 30 minutes.

Filling Preparation

Prepare the filling

Boil the diced potatoes until tender, about 15 minutes. Drain and mash. In a skillet, melt butter over medium heat, add the chopped onion, and sauté until translucent. Mix the onions into the mashed potatoes and season with salt and pepper. Allow to cool.

Assembly

Assemble the pierogies

Roll out the dough on a floured surface until thin. Cut into circles using a cookie cutter or glass. Place a tablespoon of filling in the center of each circle. Fold over and pinch to seal. Repeat with remaining dough and filling.

Cooking

Cook the pierogies

Bring a pot of salted water to a boil. Drop in pierogies and cook until they float to the surface, about 3-5 minutes. Remove with a slotted spoon and set aside.

Prepare the toppings

In a skillet, cook the chopped bacon until crispy. Remove and drain on paper towels. In the same skillet, add sliced onions and beer, cooking until onions are caramelized.

Serve

Serve pierogies topped with bacon, beer-braised onions, shredded Provolone cheese, and a dollop of sour cream garnished with chives.