Potato Pierogies

Description
I used to help my mother make pierogies every spring for Easter and every fall for Thanksgiving.. they're time consuming to make, but well worth the effort!

Ingredients

 * 1 large egg
 * 2 tablespoons sour cream
 * 1 cup milk
 * 4 1/2-5 cups all-purpose flour
 * 4 tablespoons unsalted butter, melted
 * 5 lbs baking potatoes, peeled and quartered (about 10 medium potatoes)
 * 1/4 lb unsalted butter, melted
 * 2 ounces Cheddar Cheese, grated (about 1/2 cup)
 * 4 ounces cream cheese
 * coarse salt
 * fresh ground black pepper
 * 2 tablespoons cornmeal

Directions

 * In a medium bowl, whisk the egg.
 * Add the sour cream, and whisk until smooth.
 * Add the milk and 1 cup water, and whisk until combined.
 * Slowly add about 3 cups flour, and stir with a wooden spoon to combine.
 * Turn dough out onto a well-floured surface, and work in about 1 cup flour as you knead.
 * Use a plastic scraper to lift the dough as it will stick to the counter before the flour is worked in. Continue kneading for about 8 to 10 minutes, working in another 1/2 cup flour.
 * The dough should be elastic and no longer sticky.
 * Be careful not to add too much flour as this will toughen the dough.
 * Place dough in a lightly floured bowl, and cover with plastic wrap; set aside while you prepare the filling.
 * Cook potatoes in salted boiling water until fork-tender.
 * Drain, and mash with a Potato masher.
 * Add melted butter and cheeses, and continue to mash until well-incorporated.
 * Season with salt and pepper to taste.
 * Place a large pot of salted water over high heat, and bring to a boil.
 * Lay a clean linen towel on your counter, and evenly distribute cornmeal on it to prevent sticking.
 * On a floured surface, roll out dough to about 1/8-inch thickness.
 * Using a 2 1/2-inch-diameter glass or cookie cutter, cut out as many circles as possible.
 * Gather dough scraps together, roll out again, and continue cutting.
 * Form filling into 1 1/2-inch balls, and place a ball in the center of each dough circle.
 * Holding a circle in your hand, fold dough over filling, and pinch the edges, forming a thoroughly sealed crescent.
 * Transfer to linen towel.
 * Continue until all dough circles are filled.
 * Add pierogi to the boiling water in batches.
 * They will sink to the bottom of the pot, then rise to the top.
 * Once they rise, let them cook for about 1 minute more.
 * Meanwhile, drizzle platter with melted butter.
 * Remove pierogi from pot, and transfer to platter to prevent sticking.
 * Serve immediately.