01 -
Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
02 -
In a large skillet over medium heat, heat the olive oil. Add the sliced onions and sauté until softened and golden brown, about 5-7 minutes.
03 -
Add the sliced kielbasa to the skillet and cook for another 4-5 minutes, until lightly browned. Remove from heat.
04 -
In a large bowl, whisk together sour cream, cream cheese, milk, garlic powder, black pepper, and paprika until smooth and combined.
05 -
Place the frozen pierogies in the prepared baking dish. Pour the cream sauce over them and gently toss to coat. Add the cooked onions and kielbasa on top and mix slightly to distribute.
06 -
Sprinkle shredded cheddar cheese evenly over the top of the mixture.
07 -
Cover the dish with foil and bake for 20 minutes.
08 -
Remove foil and bake for another 10-15 minutes, until the cheese is melted and the dish is bubbly.
09 -
Sprinkle with chopped parsley before serving.