01 -
Coat the interior of the slow cooker with non-stick cooking spray to prevent sticking.
02 -
Arrange half of the frozen pierogi at the base of the slow cooker. Scatter half the sliced kielbasa and half the chopped onion evenly over the pierogi.
03 -
In a mixing bowl, whisk together the condensed cream of mushroom soup, sour cream, and melted butter until smooth.
04 -
Spread half of the creamy sauce mixture evenly over the layered pierogi, kielbasa, and onion.
05 -
Repeat the layers with the remaining pierogi, kielbasa, onion, and finish by spreading the rest of the sauce mixture on top.
06 -
Cover and cook on low heat for 4 to 5 hours or until the pierogi are tender.
07 -
During the last 30 minutes of cooking, remove the lid briefly and sprinkle the shredded cheddar cheese over the casserole. Replace the lid and continue cooking until the cheese is melted.
08 -
Season with salt and black pepper to taste. Serve hot, garnished with chopped fresh chives.