Prepare the Ingredients:

1. Slice the Kielbasa: Slice the kielbasa into ¼-inch thick rounds. Set aside.
2. Chop the Onion: Finely chop the onion and set aside.
3. Grate the Cheese: Grate the cheddar cheese (or your preferred cheese blend) if it’s not pre-shredded.

Assemble the Casserole:

4. Layer the Ingredients: In a greased 6-quart crockpot, add a layer of frozen pierogis. Top with a layer of kielbasa slices and a sprinkle of chopped onion.
5. Add the Creamy Sauce: In a bowl, mix together the cream of mushroom soup, sour cream, garlic powder, onion powder, salt, and pepper until smooth.
6. Pour the Sauce: Pour the creamy sauce mixture over the layered pierogis and kielbasa, spreading it evenly with a spatula.
7. Top with Cheese: Sprinkle the shredded cheddar cheese evenly over the top of the casserole.

Cook the Casserole:

8. Cook on High: Cover the crockpot and cook on high for 3.5 hours, or until the pierogis are tender and the cheese is melted and bubbly.
9. Check for Doneness: Check the casserole after 3 hours to ensure the pierogis are tender and the cheese is fully melted. If needed, cook for an additional 30 minutes.

Serve:

10. Garnish and Serve: Once cooked, garnish with freshly chopped parsley for a pop of color and freshness. Serve hot and enjoy!