Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with olive oil.

Slice the smoked beef kielbasa into ½-inch rounds and halve each round. Dice the two large yellow onions.

In a mixing bowl, whisk together the condensed cream of mushroom soup and cream of chicken soup until smooth. Then, incorporate the sour cream, milk, garlic powder, onion powder, and dried dill.

Heat olive oil in a large skillet over medium-high heat. Add the sliced kielbasa and brown it for about 5-7 minutes.

Add unsalted butter to the skillet. Toss in the diced onions and sauté for 10-15 minutes until they are softened and lightly caramelized.

Combine the caramelized onions with the browned kielbasa in the skillet.

Spread one-third of the creamy sauce across the bottom of the greased baking dish. Layer half of the frozen potato and cheddar pierogi over the sauce.

Add half of the kielbasa and onion mixture over the pierogi, followed by a layer of 1 ½ cups shredded sharp cheddar cheese and ¾ cup shredded Monterey Jack cheese.

Repeat the layering process with the remaining sauce, the rest of the frozen pierogi, and the remaining kielbasa mixture.

Pour the final third of the creamy sauce evenly over the top of the casserole and dot with the remaining butter.

Cover the baking dish with aluminum foil and bake for 45 minutes covered, then uncover and bake for an additional 20-25 minutes until the top is golden brown and bubbly.

Let the casserole rest for 10-15 minutes before serving and garnish with chopped fresh parsley.