Sift the flour into a bowl. Add sugar, salt, yeast and butter, chop everything together.
Add an egg and milk.Quickly knead the dough (if necessary, sprinkle with flour).The dough should be flexible, not too hard and not sticky.
Roll out the dough thinly, carve out the desired shape and apply the filling of choice. Fold the dough over, press the edges firmly together.
Line a baking tray with parchment paper. Place assembled pierogi on the tray. Cover with a cloth and allow to rest in a warm place for 20-25 minutes.
Preheat the oven to 180°C/356°F. Cover pierogi with egg wash and bake for 20 minutes until golden.