• Step 1: Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish with nonstick cooking spray.
• Step 2: In a large bowl, combine the cubed chicken, cream of chicken soup, sour cream, 1/2 cup of the shredded cheddar cheese, milk, garlic powder, onion powder, and black pepper. Mix well until all the ingredients are evenly distributed.
• Step 3: Spread the chicken mixture in the prepared baking dish. Top with the thawed hashbrowns, spreading them evenly over the chicken layer.
• Step 4: Drizzle the melted butter over the hashbrowns, then sprinkle the remaining 1/2 cup of shredded cheddar cheese on top.
• Step 5: Bake the casserole for 45-55 minutes, or until the hashbrowns are golden brown and the cheese is melted and bubbly. Allow the casserole to cool for 5-10 minutes before serving.