Follow the steps in order for the best result.
To prepare the filling, begin by shredding the cheddar cheese and setting it aside.
Next, peel, cube, and cook the potatoes until they are tender. Drain them thoroughly.
Place half of the cooked potatoes into a mixing bowl (a KitchenAid mixer works great). Add the shredded cheese, and then top with the remaining potatoes.
Beat the mixture well, and taste to ensure the seasoning is to your liking. Let the filling cool completely.
The filling can be made a day in advance. Ensure it cools completely before covering to prevent it from sweating and becoming watery.
For the dough, place all the dough ingredients into a food processor bowl, starting with the flour.
Process until the dough forms a ball and the sides of the processor are clean. Shape the dough into a flat disc. If the dough is a little sticky, use flour to help shape it. Wrap the disc in plastic wrap and let it rest for 30 minutes.
Flour your working surface and roll the dough out fairly thin. This recipe should yield approximately 38 to 40 pierogies.
Cut the dough into circles using a wide-mouth canning jar top or any similarly sized cutter. Wet one side of each circle and place a walnut-sized portion of the potato mixture onto the center.
Fold the dough over and pinch the edges well to seal. Place each pierogi on a parchment-lined cookie sheet, ensuring they are separated from each other.
Continue this process until all the dough is used up.
Bring a 5-quart pot of water to a boil. Using a wooden spoon, stir the water as you gently place the pierogies into the boiling water. Cook only about 10 at a time.
Let them rise to the surface and continue to cook for about 2 minutes.
Have a large bowl of cold water ready. Remove the pierogies from the boiling water and place them in the cold water for several minutes.
Drain each pierogi well to remove any excess water, then roll them in vegetable or canola oil, shaking off any excess. This prevents them from sticking together.
You can use quart-sized Ziploc bags to bag about 10 pierogies per bag. Lay them flat on a cookie sheet, and at this point, they can be frozen until ready to use.
When preparing about 10 or 12 pierogies (do not overcrowd the pan), melt 1/2 to 1 stick of butter or margarine in a large coated frying pan. Add 1 cup of diced onions and sauté until they are soft and golden, but not brown.
Add about 3 tablespoons of water and lay your unfrozen pierogies on top. Cover the pan with a lid and cook on low heat until they become soft and puffy. Be careful not to cook them too quickly, as the bottoms will brown.
When ready to serve, pour the pierogies onto a dinner-sized plate. It's easier to scoop them out than from a bowl.
Enjoy these delicious homemade pierogies!