1. Spray the inside of your crockpot with cooking spray to prevent sticking.
2. Layer the frozen pierogis at the bottom of the crockpot.
3. Evenly distribute the sliced kielbasa over the pierogis.
4. In a medium bowl, mix together the shredded cheddar cheese, sour cream, condensed cream of mushroom soup, milk, garlic powder, and black pepper.
5. Pour the mixture over the pierogis and kielbasa, spreading it out with a spatula to ensure everything is covered.
6. Cover and cook on low for 4-5 hours, or until the pierogis are tender and the sauce is bubbly. You’ll know it’s ready when the cheese is melted and slightly golden around the edges.
7. If desired, sprinkle with fresh parsley before serving for a pop of color and freshness.

My grandmother always said the secret to a good casserole is patience, and this dish is no exception. Letting it cook slowly allows the flavors to meld beautifully, making each bite more delicious than the last.