Preheat Oven: Set your oven to 350°F and lightly grease a 9x13-inch baking dish.
Mix Ingredients: In a large mixing bowl, combine the shredded hash browns, 1 cup of the melted butter, cream of chicken soup, sour cream, mayonnaise, grated cheddar cheese, onion powder, garlic powder, salt, and pepper. Stir everything together until it's well-mixed.
Transfer to Baking Dish: Pour the mixture into the prepared baking dish, spreading it out evenly.
Prepare the Topping: In a separate bowl, mix together the corn flakes with ½ cup of melted butter until coated.
Top the Casserole: Sprinkle the buttery cornflake mixture evenly over the hash brown mixture in the baking dish.
Bake: Cover with foil and place the dish in the preheated oven. Bake for 45 minutes covered and 15 minutes uncovered for a total of one hour, or until the top is golden brown and the sides are bubbly.
Serve: Once baked, remove the casserole from the oven and let it cool for a few minutes. Then, serve warm.