Preheat your oven to 375°F. Lightly grease a 9×13″ baking dish and set aside.

In a hot skillet, sear the kielbasa slices over medium heat until they develop a golden crust, about 3 minutes. Transfer to the prepared baking dish.

Add a pat of butter to the same skillet. Toss frozen pierogies for 2 minutes per side—this quick pan-fry adds a slight crisp before baking. Nestle them around the kielbasa.

Whisk together cream cheese and sour cream until smooth. Stir in broth, onion powder, garlic powder, salt, pepper and half of each cheese until silky.

Pour the sauce evenly over the pierogies and kielbasa. Sprinkle the remaining cheddar and mozzarella on top.

Cover with foil and bake 30 minutes. Uncover and bake another 10 minutes until bubbly and golden.

Let rest 5 minutes, then garnish with green onions and serve.