hash brown casserole recipe

Ingredients: 1 (30-ounce) bag frozen shredded hash browns, thawed 1 can (10.5 ounces) cream of chicken soup 1 cup sour cream 1/2 cup unsalted butter, melted 1 small onion, finely chopped 2 cups shredded cheddar cheese 1/4 teaspoon garlic powder Salt and pepper, to taste 1 cup crushed cornflakes or breadcrumbs (optional topping) 2 tablespoons unsalted butter, melted (for topping, optional)