Preheat the Oven:
Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
Mix the Ingredients:
In a large bowl, combine the thawed hashbrowns, cream of chicken soup, sour cream, cheddar cheese, melted butter, onion, garlic powder, salt, and pepper. Stir until everything is well mixed.
Transfer to the Dish:
Spread the mixture evenly into the prepared baking dish.
Add Optional Topping:
If using, mix crushed cornflakes or Ritz crackers with 2 tbsp melted butter and sprinkle over the top of the casserole.
Bake:
Bake uncovered for 45–50 minutes, or until hot and bubbly and the top is golden brown.
Cool Slightly & Serve:
Let cool for about 5–10 minutes before serving. Enjoy!