Russian Potato Piroschkis with Mushroom Filling

For the dough, scrub and peel potatoes and cook in boiling salted water until knife-tender, about 30 minutes. Drain potatoes and let cool.

Finely grate potatoes. Separate eggs, beat whites and set aside. Mix egg yolks, butter, flour and 2 teaspoons salt into potatoes. Knead potato mixture into a dough.

For the filling, scrub mushrooms and chop finely.

Peel shallot and garlic and dice finely. Melt butter in a skillet, sauté shallot and garlic and add mushrooms. Cook mushroom mixture over medium heat, stirring occasionally, until liquid is evaporated, about 8 minutes. Stir thyme into filling and season liberally with salt and pepper. Mix parsley into filling, remove from heat and let cool slightly.

On a floured surface, roll out potato dough about 0.5 cm thick (approximately 1/8 inch thick). Sprinkle dough with flour and cut out 16 circles about 10 cm diameter (approximately 4 inches diameter). To assemble piroschkis, heap about 1 teaspoon filling on each circle and brush circle edges with egg white. Fold dough circles in half over filling and press edges firmly with a fork to seal.

Brush piroschkis with egg white and coat with breadcrumbs.