Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch casserole dish with butter or nonstick spray.

In a medium skillet over medium heat, melt 1 tablespoon of butter. Add chopped onion and cook until translucent, about 3 minutes. Stir in garlic and cook another 30 seconds—aroma should fill the kitchen.

In a large bowl, combine sour cream (or Greek yogurt), cream of chicken soup, melted butter, smoked paprika, onion powder, salt, and pepper. Whisk until smooth; this binds your cheesy potatoes into a luscious casserole dish.

Gently stir in the thawed hashbrowns, sautéed onion mixture, and 1½ cups of cheddar cheese. Reserve the remaining cheese and all Parmesan for topping. Overmixing can break down potato flakes, so stir just until ingredients are evenly coated.

Spread the mixture into your prepared dish in an even layer. Sprinkle the remaining cheddar and all Parmesan cheese on top. This double-cheese approach gives you that irresistible golden crust.

Bake uncovered for 40–45 minutes, until the edges bubble and the top is lightly browned. If you crave extra crisp, switch to broil for 2 minutes—just watch closely so it doesn’t burn.

Remove from oven and let rest 5–10 minutes. This brief chill helps the casserole set and makes slicing neater. Sprinkle fresh chives or parsley for a pop of color before serving.