Preheat oven to 350°F. Lightly spray a 9" x 13" baking dish with nonstick spray; set aside.
Hashbrown Casserole: Place hashbrowns in a large mixing bowl; set aside.
In a medium bowl, combine shredded cheese, sour cream, cream of chicken soup, melted butter, dried onion, salt, pepper, and garlic powder.
Add cheese mixture to hashbrowns and fold to combine. Transfer mixture to prepared baking dish and spread into an even layer.
Corn Flakes Topping: In a small bowl, combine melted butter with crushed corn flakes. Sprinkle over top of casserole.
Bake & Serve: Cover dish with foil and bake for 60 minutes. Remove foil and bake an additional 5 to 10 minutes, or until casserole is thoroughly hot. If you'd like an extra crunchy topping, set the dish under the broiler for a few minutes. Top with chopped green onions or chives. Serve hot!
