Preheat oven to 375°F (190°C). Grease a 9×13 baking dish with non-stick spray or butter.
Layer half the potatoes, half the kielbasa, half the onions, and half the cheese.
Repeat the layers with the remaining potatoes, kielbasa, onions, and cheese.
In a bowl, whisk soup, milk, melted butter, garlic powder, salt, and pepper until smooth.
Pour the sauce evenly over the casserole, covering all layers.
Cover the pan tightly with foil and bake for 1 hour.
Remove the foil, sprinkle breadcrumbs on top, and bake another 10–15 minutes until golden and crispy.
Optional: broil for 1–2 minutes for extra crunch (watch closely).
Let rest 5–10 minutes before serving, then garnish with parsley.
