Buttery Sauerkraut Pierogi with Caramelized Onions

In a large bowl, whisk together the flour and salt, then stir in the egg, sour cream, and softened butter until a shaggy dough forms.

Turn the dough onto a floured surface and knead for 5 to 7 minutes until it becomes smooth and elastic, then wrap in plastic and rest for 30 minutes.

While the dough rests, squeeze any excess moisture from the sauerkraut and finely chop it, then set it aside.

Heat 2 tablespoons of vegetable oil in a skillet over medium heat, add the chopped onion, and sauté for 5 minutes until soft and translucent.

Add the chopped sauerkraut and black pepper to the skillet, cooking for 10 minutes until the mixture is dry and lightly browned, then let it cool.

Roll the rested dough on a floured surface to about 1/8-inch thickness, then use a 3-inch round cutter to stamp out circles.

Place 1 teaspoon of the cooled sauerkraut filling in the center of each dough circle, fold in half, and pinch the edges tightly to seal.

Bring a large pot of salted water to a gentle boil, drop the pierogi in batches, and cook for 2 to 3 minutes after they float to the surface.

Melt 4 tablespoons of butter in a clean skillet over medium heat, add the sliced onion, and cook for 10 minutes until golden and caramelized.

Transfer the drained boiled pierogi directly into the skillet with the caramelized onions and fry for 2 to 3 minutes per side until crisp and golden brown before serving.