Knysh with potatoes

Ingredients:

• 4 cups mashed potatoes
• 2 cups thinly sliced ​​and caramelized onions
• 1 egg
• 1/2 cup finely chopped parsley, plus more for garnish
• Salt and ground black pepper
• 1/2 cup vegetable oil
• 1 cup of water
• 1 tbsp. table vinegar
• 1/2 tsp salt
• 4 cups of wheat flour
• 1/2 cup egg for brushing

Preparation:

1. In a bowl, combine the onion, potato, egg, and parsley. Season with salt and pepper.
   
   For the test: In a bowl, combine the oil, water, vinegar, and salt. Add flour, 1 cup at a time, and knead the dough into a ball. Form it into 4 balls and let it rest, covered with a towel, for about 30 minutes.
2. Preheat oven to 190°C.
   
   Roll each dough ball as thinly as possible to form a flat rectangle. Dust the dough with flour and cover with parchment paper. Let it rest for 15 minutes. Use your hands to stretch the dough until it is very thin. Spread 1/4 of the filling over one-third of the dough, leaving a 2.5 cm border.
   
   Using parchment paper, roll the dough into a log, brushing the surface with oil a couple of times as you roll. Using the edge of your hand instead of a knife, divide the roll into 5 cm-long knishes. Pinch the open ends. Repeat with the remaining balls and dough. You should have 24 pirozhki.
3. Place the knyshi flat-side down on a greased baking sheet, spacing them 5 cm apart. Bake the knyshi in batches. Brush them with egg wash. Bake for 25-30 minutes, until golden brown. Place the knyshi on a serving plate and sprinkle with aromatic essence and parsley.