Grandma's Polish Perogies

Instructions

• Prepare the dough: Stir flour and salt together in a large bowl. Whisk sour cream, eggs, egg yolk, butter, and oil in a separate bowl. Stir wet ingredients into flour until well blended and dough comes together. Cover the bowl with a towel, and let stand for 15 to 20 minutes.
• Meanwhile, prepare the filling: Place potatoes into a pot, and fill with enough water to cover. Bring to a boil, and cook until tender, about 15 minutes.
• Drain potatoes, and mash with shredded cheese and cheese sauce while still hot. Season with onion salt, salt, and pepper. Set aside to cool.
• Separate pierogi dough into two balls. Roll out one ball at a time on a lightly floured surface until it is thin enough to work with, but not too thin so that it tears, between 1/8- and 1/4-inch thick. Cut into circles using a cookie cutter, pierogi cutter, or a glass, 3- to 4-inches in diameter.
• Assemble the perogies: Brush a little water around the edges of the circles, and spoon some filling into the center. Fold the circles over into half-circles, and press to seal the edges with fingers, or use a fork for crimped edges.
• Place perogies on a cookie sheet, and freeze. Once frozen, transfer to freezer storage bags or containers.
• To cook the perogies: Bring a large pot of lightly salted water to a boil. Lower perogies into the water in batches. Cook until they float to the top, about 5 minutes. Do not boil too long, or they will be soggy. Remove with a slotted spoon.