Combine flour, water, egg, oil, and salt in the bowl of a " target="_blank">stand mixer fitted with a dough hook attachment. Add additional flour if needed to form a cohesive, but still slightly sticky dough.

Knead in the mixer with the dough hook on medium speed for 10 minutes until the dough can stretch without breaking.

Cover the bowl with plastic wrap or a kitchen towel and let the dough rest for 1 hour.

While dough is resting, peel and chop the potatoes into ½ inch chunks. Boil in salted water until tender when pierced with a fork, about 8 minutes.

Drain the potatoes and transfer to a heatproof bowl. Add the cheese while the potatoes are still hot and mash with a potato masher until combined and there are no large potato chunks. Slightly chunky is okay, but chunks larger than ¼ inch may make it harder to form the pierogies.

When cool enough to handle, form the potato/cheese mixture into 60 1-1¼ inch balls. Set aside until dough is ready.

Prepare a floured surface for rolling out dough.

Halve the dough and roll out to ⅛” thick.

Using a 3” diameter round cookie cutter, cut out circles of dough. Gather the scraps and reroll to cut more circles. Keep flouring the surface as needed. If the dough shrinks back a lot, let it rest for 5 minutes, then continue rolling. Do the same for the other half of the dough. You should get about 60 circles total. It helps to have a friend for this step!

To shape the pierogies, hold a circle of dough in your palm and place the ball of potato/cheese filling in the center. Dip a finger on your other hand into a small bowl of water, and wet the dough around the bottom half of the rim. Cup your hand gently to start to fold the pierogie closed, pinching the dough together from one corner to the other. Be sure to avoid trapping any air inside the pierogie. You want at least ¼ inch of pinched edge around the pocket. Crimp the edge with a fork if desired.

At this point you can freeze the pierogies on a parchment lined baking sheet for 30 minutes, and then transfer into an airtight container or bag for freezer storage. Pierogies will keep in the fridge for several months.

If you are cooking all the pierogies right away, boil the pierogies is salted water for 4-5 minutes, or until the pierogies float to the surface.

Heat a tablespoon of butter in a fry pan until hot, brown the pierogies in batches until nicely browned on both sides. Serve with strained yogurt as an appetizer, or as a side with sausage and cabbage.