Stir the flour with salt in a medium/large bowl.

Warm the water with butter/oil in a small pot until very warm but not boiling.

Add the liquid to the bowl. Stir the dough with a spoon until roughly combined.

Knead the dough by hand or with a stand mixer fitter with a hook dough attachment, until it's soft and smooth (it will take about 5 minutes with the mixer). When you follow the recipe (especially if you weigh the ingredients, instead of using measuring cups), the dough should be perfect, but if for some reason it’s not, add some water if it’s too dry, or a little bit of flour if it’s too wet. If the dough already forms a ball, is relatively smooth, but still tough, it means that it’s not ready, it must be further kneaded until soft and elastic (after resting time it will be even softer).

Wrap the dough with plastic foil and leave to rest for 30 minutes. While the dough is resting, make the filling. You can make it in the same bowl.

Mix the egg yolks with sugar until combined.

Add all the other ingredients and mix until combined. I'm using my stand mixer with a paddle-shaped attachment, but you can just stir the ingredients with a fork, if you don't have a mixer.

Divide the dough into 2 parts.

Roll out the first part of the dough on a lightly floured surface (I like silicone rolling mats). Cut out rounds with pierogi cutter/biscuit cutter/a glass. The dough should be rolled out thinly. If the dough is hard to roll out, set it aside for about 5-10 minutes to rest.

Gather scraps, cover with plastic wrap and set aside.

Scoop some filling with a teaspoon and place on each round.

Fold the dough over the filling to create a half-moon shape. Press edges together, sealing and crimping with your fingers.

Place the pierogi apart on a towel lightly sprinkled with flour, cover loosely with a kitchen cloth so that they don‘t dry out.

Repeat with the remaining dough.

Bring a large pot of salted water to a boil.

Cook the pierogi in batches (for a 8-inch (21 cm) pot I cook about 10-12 dumplings at a time). When they float to the water surface cook them for 1-2 minutes more, then remove from the water with a slotted spoon. The cooking time will depend on the thickness of the dough.

Drain well and transfer onto a plate.

Enjoy!