In a large bowl, combine flour and salt. Create a well in the center and add the egg. Gradually mix in water until a dough forms. Knead until smooth, then cover with a towel and let rest for 30 minutes.

In a skillet over medium heat, cook the ground beef until browned. Drain excess fat. Add the diced onion and minced garlic, cooking until the onion becomes translucent.

Stir in the cumin, chili powder, salt, and pepper, and remove from heat. Mix in the shredded cheddar cheese and half of the enchilada sauce until well combined.

Divide the pierogi dough into four sections. On a floured surface, roll one section out to about 1/8 inch thickness. Use a round cutter (or glass) to cut circles from the dough.

Place about a tablespoon of the beef filling in the center of each dough circle. Moisten the edges with a bit of water and fold over to create a half-moon shape. Press the edges together to seal, ensuring no filling escapes. Repeat with remaining dough and filling.

Bring a large pot of salted water to a boil. Drop pierogies in batches, cooking for about 3-5 minutes or until they float to the top. Remove with a slotted spoon and drain on a paper towel.

Preheat your oven to 350°F (175°C). In a greased baking dish, spread a layer of the remaining enchilada sauce evenly on the bottom. Lay the cooked pierogies in a single layer and cover with more enchilada sauce. Sprinkle the top with additional shredded cheese.

Cover the baking dish with aluminum foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes until the cheese is bubbly and golden.

Remove the casserole from the oven and let it cool slightly. Garnish with sliced green onions and serve warm with a dollop of sour cream.