Prepare the Crockpot: Spray the inside of your crockpot with non-stick cooking spray or lightly grease it.

Layer the Pierogies: Place the frozen pierogies in an even layer at the bottom of the crockpot.

Add the Kielbasa and Vegetables: Layer the sliced kielbasa over the pierogies, followed by the chopped onion and minced garlic.

Mix the Sauce: In a medium bowl, whisk together the condensed cream of mushroom soup, sour cream, chicken broth, black pepper, paprika, and dried thyme. Stir in 1 cup of the shredded cheddar cheese.

Assemble the Casserole: Pour the sauce mixture over the pierogies, kielbasa, and vegetables in the crockpot. Gently stir or spread the sauce to ensure everything is evenly coated.

Cook: Cover the crockpot and cook on low for 4-5 hours, or on high for 2-3 hours, until the pierogies are tender and the casserole is heated through.

Add More Cheese: About 15 minutes before serving, sprinkle the remaining 1 cup of shredded cheddar cheese over the top of the casserole. Cover and allow the cheese to melt.

Garnish and Serve: Once the cheese is melted, garnish with fresh parsley or green onions if desired. Serve the pierogi casserole hot.