- 2 1/2 cups all-purpose flour
- 1 cup sour cream
- 1 large egg, beaten
- 1 large egg yolk, beaten
- 4 tablespoons unsalted butter, melted
- 1/2 teaspoon salt
- 3/4 pound medium Yukon Gold potatoes
- 3 tablespoons sour cream
- 1 1/2 tablespoons Dijon mustard
- 4 tablespoons unsalted butter, softened
- Salt and freshly ground pepper
- Vegetable oil, for coating
- 1 tablespoon chopped parsley
- In a large bowl, mix the flour with the sour cream, egg, egg yolk, butter and salt. On a lightly floured work surface, knead the dough briefly until smooth. Cover the dough with plastic wrap and let rest at room temperature for 15 minutes.
- In a medium saucepan, cover the potatoes with water and boil until tender, about 12 minutes. Drain the potatoes and peel them as soon as possible. In a bowl, mash the potatoes with the sour cream, mustard and 2 1/2 tablespoons of the butter until smooth. Season with salt and pepper.
- Bring a large pot of salted water to a boil. On a floured work surface, roll out the pierogi dough 1/8 inch thick. Using a 3 1/2-inch biscuit cutter, stamp out 20 rounds. Brush off any excess flour and moisten the edge of each round with water. Place a level tablespoon of the potato filling on one side of each round, leaving a 1/4-inch border. Fold the dough over the filling to form half-moons and press the edges firmly to seal.
- Cook the pierogies in the boiling water until tender, about 5 minutes. Drain well and transfer to a large, shallow dish. Add a little vegetable oil and toss to coat lightly.
- In a large skillet, melt the remaining 1 1/2 tablespoons of butter. Add the pierogies and cook over moderate heat, turning once, until browned, about 3 minutes per side. Transfer the pierogies to a platter. Season with salt and pepper, sprinkle with the parsley and serve.
The pierogies can be prepared through Step 4 and refrigerated for up to 3 days.