Pierogies with Potato Filling

Make the filling. Peel the potatoes and cut them into chunks. Cover with water, add salt, and cook until tender (about 25–30 minutes from the moment the water comes to a boil).

Peel the onion and finely chop it.

Heat vegetable oil in a skillet. Fry the onion over high heat for about 10–15 minutes until deeply golden (stir frequently to prevent burning).

Drain the cooked potatoes. Add the butter, season generously with pepper, and mash with a potato masher.

Add half of the fried onion from the skillet and mix well. Taste and adjust salt and pepper as needed (the filling should be slightly saltier than regular mashed potatoes).

Divide the filling into four equal portions.

Make the dough. Sift 2/3 of the flour into a bowl, add the salt, and stir to combine.

Add the baking soda to the kefir and stir to combine.

Add the egg to the flour, then pour in the kefir. Knead the dough by hand (it will still be quite sticky at this stage).

Spread the remaining flour on a cutting board (or your work surface). Turn the dough out onto the flour and knead thoroughly by hand until all the flour is incorporated. The finished dough should not stick to your hands (add a little more flour if needed). Wrap the dough in a plastic bag (to keep it from drying out) and let it rest for 20 minutes.

Start shaping the pierogies. Cut off one quarter of the dough and return the rest to the bag.

Roll the dough into a thick log (about 5 cm in diameter). Cut it into 12 rounds (for even pieces, score the log with a knife starting from the middle).

Flatten each round with your hands and roll it out with a rolling pin into a thin circle about 8 cm in diameter (1–2 mm thick).

Place a heaping teaspoon of filling in the center of each circle. Moisten the edges of the dough with your finger (dip your finger in a cup of water).

Fold the dough over the filling and pinch the edges together to seal.

If desired, crimp the edge in a wavy pattern. Place the finished pierogies on a flour-dusted board.

Cook the pierogies. Bring a pot of water to a boil and add salt. Drop the pierogies in one at a time. Cook for about 5 minutes after they float to the surface.

Remove the cooked pierogies with a slotted spoon and transfer to a plate. Coat generously with butter and top with the remaining fried onion. These potato pierogies are also great served with sour cream.