Pour a cup of warm milk in a bowl, add a pinch of salt and the egg, then whisk together.
1 cup warm milk, 1 pinch salt, 1 egg
In a separate bowl, mix together flour and dry yeast.
3 cups all-purpose flour, 1 tsp dry yeast
Start adding the flour with the yeast mixture into the bowl with wet ingredients. To make the job easier, use an electric mixer with a hook attachment.
Add ½ cup of flour at a time and mix until the dough forms into a ball. You might need less than 3 cups of flour, that’s the reason why we don’t add it all at once.
3 cups all-purpose flour
When the dough is formed, cover the bowl with a plastic wrap or a towel and place in a warm place for the dough to rise. Leave it for 2 hours or until the dough doubles in size and is soft and easy to work with.
While the dough rises, prepare the potato filling.
For the potato filling:
Peel the potatoes and onion.
3 medium potatoes,, 1 onion,
Cut potatoes in pieces, place them in a pot, cover with cold water, and cook covered for 20 minutes until potatoes are tender.
Meanwhile, dice the onion and sauté in butter until onion is soft.
1 onion,, 2 Tbsp butter
Mash potatoes with a potato masher, add salt, pepper, sautéed onions, and ½ cup of water and mix well. The filling is ready to use.
1 onion,, salt,, black pepper,, 1 cup warm milk
Put together the piroshki:
Now you can start shaping your piroshki. Pinch off pieces approximately the size of a golf ball (keep the rest of the dough in a bowl covered while working on each piece).
Roll the piece into a disk shape, about 3 ½ inches in diameter, adding flour when needed.
Place a tablespoon of the filling on the center of the dough.
Fold the dough over the filling and firmly pinch the edges to seal.
Place formed piroshki on a lightly floured surface and let them sit for about 5-10 minutes.
In a large heavy skillet heat the oil and fry piroshki in batches on both sides until golden brown (sealed side down).
2 Tbsp oil,
Remove and drain piroshki on a plate lined with a paper towel.
Notes
Refrigerate cooked piroshki for up to 3-4 days. Reheat them in the oven or microwave before serving.