• Mix the flour with the confectioners' sugar until combined, then add the egg and egg yolk and stir with a knife.
• Slowly add the lukewarm water and oil, mixing until a dough starts to form.
• Tip the dough onto a lightly floured board and knead for about 5 minutes, just until the mixture comes together with no lumps and feels smooth.
• Wrap the dough in plastic wrap and leave it to rest for at least 30 minutes in the refrigerator.

For the Sweet Cream Cheese Filling:

• Mix all the sweet cream cheese filling ingredients (cream cheese, egg yolks, sugar, vanilla) together until well combined, then chill in the refrigerator, too, for an hour.

To Assemble:

• When you are ready to make the pierogi, bring a large pot of water to a rolling boil.
• Roll out your dough on a board dusted with a little confectioners' sugar. You are aiming for the dough to be around 1/8 inch (3 millimeters) thick.
• Use a 3 1/2 inch (9 centimeter) pastry cutter or a glass tumbler to cut out circles of dough.
• Take your cheese filling out of the refrigerator and place a tablespoon of filling onto each circle.
• Working quite quickly, take each circle in your hand, fold the dough over to form a semi-circle, and pinch the dough along the edge so that each dumpling is well sealed.
• Place each one back on the board dusted with confectioners' sugar.
• To cook the dumplings, carefully drop them into the boiling water, in batches of 5 at a time, until each one floats to the surface. They will only take a minute or so to cook.
• Carefully remove each one with a slotted spoon and place on a large platter.
• Serve with a dusting of confectioners' sugar, a drizzle of melted butter, and some sweetened sour cream.