Ukrainian Zenia’s Potato Varenyky

Ingredients
FOR THE FILLING salt & freshly ground black pepper
 * 1 	small Onion, finely chopped
 * 2 	tablespoons butter
 * 2 	cups warm mashed potatoes
 * 3/4 	cup shredded Cheddar Cheese

FOR THE DOUGH

melted butter
 * 2 	cups all-purpose flour
 * 1 	teaspoon salt
 * 2 	egg yolks
 * 1/2 	cup cold mashed potatoes
 * 1 	tablespoon melted butter
 * 1/2 	cup cool water (approx.)

Directions

 * PREPARE THE FILLING FIRST: Saute the Onion in the butter until softened, about 6 minutes.
 * Combine with the potatoes and Cheese and mix well.
 * Season with salt and pepper.
 * Let cool thoroughly before using.
 * (The filling can be made a day ahead and kept covered and refrigerated.
 * Bring to room temperature before using.).
 * TO MAKE THE DOUGH: Combine the flour and salt in a large mixing bowl.
 * Add the egg yolks, mashed potatoes, melted butter and just enough of the water to form a medium-soft dough.
 * Turn the dough out onto a lightly floured surface and knead until smooth. (Too much kneading will make the dough tough.).
 * Divide the dough in half and cover with an inverted bowl.
 * Let stand for 10 minutes.
 * Roll out the dough until it is quite thin and cut rounds about 2 to 3 inches wide with a large biscuit cutter.
 * Bring a large pot of water to a boil and add a little salt.
 * To each round of dough, add a spoonful of filling ad fold over to form a half circle.
 * Press the edges together with well floured fingers, making sure the varenyky are well sealed.
 * Transfer them to a lightly floured surface and cover them with a clean tea towel so that they do not dry out.
 * Drop a few at a time into the boiling water, stirring gently with a wooden spoon to separate them and keep them from sticking to the bottom of the pot.
 * Boil for 3 to 4 minutes, at which point they should be puffed and bobbing on the surface.
 * (The thinner the dough and the smaller the pyrohy, the quicker they will cook.).
 * Transfer with a slotted spoon to a colander, drain thoroughly and place in a warmed bowl.
 * Drizzle with melted butter and toss gently to keep them from sticking together.
 * Cover and keep warm while you cook the remaining varenyky.