Creating homemade pierogi is a rewarding experience. Follow these steps for perfect results:

1. Make the Dough: In a large bowl, combine flour and salt. Create a well in the center and add the egg. Gradually mix in warm water until a dough forms. Knead for about 5-7 minutes, until smooth. Cover and let it rest for 30 minutes.

2. Prepare the Filling: In a skillet, melt butter over medium heat. Add chopped onion and sauté until golden brown. In a bowl, combine mashed potatoes, cheddar cheese, sautéed onions, and season with salt and pepper to taste.

3. Roll Out the Dough: After the dough has rested, divide it into quarters. Roll out one quarter on a floured surface to about 1/8 inch thick. Keep the remaining dough covered to prevent it from drying out.

4. Cut the Dough: Use a round cutter or glass to cut out circles from the rolled dough, about 3 inches in diameter.

5. Fill the Pierogi: Place a teaspoon of the filling in the center of each circle. Fold the dough over to create a half-moon shape. Press the edges together firmly to seal, ensuring there are no air pockets.

6. Cook the Pierogi: Bring a large pot of salted water to a boil. Gently add the pierogi in batches (don’t overcrowd the pot). Cook until they float to the surface, about 3-4 minutes. Remove with a slotted spoon and drain.

7. Optional – Sauté the Pierogi: In a skillet, melt some butter. Add the boiled pierogi and sauté until golden and crispy on both sides.

8. Serve: Transfer the pierogi to a serving platter. Drizzle with melted butter and top with sour cream and chopped chives or green onions.