In a large bowl, combine the thawed hash browns, sour cream, cream of chicken soup, 1 1/4 cups of shredded cheddar cheese, 3 tablespoons of melted butter, the chopped onion, salt, dried parsley, and garlic powder.
In a small bowl, mix the crushed corn flakes with the remaining 1 cup of cheese and the remaining 2 tablespoons of melted butter. Sprinkle evenly over the casserole.