Creating this cheesy hash brown casserole is surprisingly easy, even for beginner cooks. Follow these simple step-by-step instructions for guaranteed success:

1. Preheat Your Oven & Prepare Your Baking Dish: Start by preheating your oven to 350°F (175°C). This ensures the oven is at the correct temperature when you place the casserole in, promoting even cooking. While the oven is preheating, lightly grease a 9×13 inch baking dish. Greasing prevents the casserole from sticking and makes serving and cleanup much easier. You can use butter, cooking spray, or even a light coating of oil.
2. Combine the Wet Ingredients: In a large mixing bowl, whisk together the cream of chicken soup and sour cream until smooth and well combined. This creates the creamy base for your casserole. Ensure there are no lumps of soup remaining for a consistent texture.
3. Melt the Butter and Sauté the Onion: In a skillet over medium heat, melt the butter. Add the chopped onion and sauté until softened and translucent, about 5-7 minutes. Sautéing the onion before adding it to the casserole mellows its flavor and prevents it from being too harsh or crunchy in the finished dish. Stir frequently to prevent burning.
4. Combine All Ingredients: Add the sautéed onions and melted butter to the bowl with the soup and sour cream mixture. Stir well to incorporate everything evenly. Next, add the garlic powder, salt, and black pepper. Mix again to distribute the seasonings throughout the base. Now, add the thawed hash browns and 1 ½ cups of the shredded cheddar cheese to the bowl. Gently fold all the ingredients together until the hash browns are evenly coated in the creamy cheese mixture and the cheese is dispersed throughout. Be careful not to overmix, as this can make the hash browns mushy.
5. Pour into Baking Dish and Top with Cheese: Pour the hash brown mixture into the prepared baking dish, spreading it evenly in a single layer. Ensure the mixture reaches all corners of the dish for even baking. Sprinkle the remaining ½ cup of shredded cheddar cheese evenly over the top of the casserole. This creates that irresistible golden-brown, cheesy crust.
6. Bake to Golden Perfection: Bake in the preheated oven for 45-55 minutes, or until the casserole is heated through, bubbly around the edges, and the cheese topping is melted and golden brown. The baking time may vary slightly depending on your oven. To check for doneness, insert a knife into the center of the casserole; it should come out hot. The edges should be nicely browned and the casserole should be bubbling.
7. Let it Rest and Serve: Once baked, remove the casserole from the oven and let it rest for 5-10 minutes before serving. This allows the casserole to set slightly, making it easier to slice and serve. Resting also helps to prevent it from being too watery. Serve hot and enjoy the cheesy goodness!