Dump flour on counter. Make a well in the center, and add the salt, the oil, and egg.

Using a fork, start mixing the egg, allowing the flour to incorporate a little at a time, until the mixture is dry and crumbly.

Add the water a bit at a time, and mix it in as you mixed in the egg. Each time, allow the mixture to become dry and crumbly before adding more water.

The mixture will have come together into a dough. Knead the dough until it is soft and smooth, about 6-10 minutes.

Wrap it in plastic wrap and let the dough rest about an hour

Roll out the dough on a lightly floured surface to about 1/8 of an inch thick and use a cookie cutter or the rim of a glass to cut out circles of dough 2 1/2 - 3 1/2 inches in diameter.

Place about 2-3 teaspoons of your filling in the center of each circle, fold over, and crimp with a fork.

Bring a large pot of water to a boil over high heat. Meanwhile, melt butter in a skillet over medium-low heat. Working with about eight pierogi at a time, place them in the boiling water, let it come back to a boil, and boil the pierogi for 5 minutes after they float to the surface.

Once boiled, remove pierogi with a slotted spoon and fry in melted butter until browned on each side, about 2-3 minutes per side.