Creating the Cheesy Potato Breakfast Casserole is simple and straightforward. Follow these steps to ensure a delicious outcome:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with cooking spray or butter.
2. Prepare Hash Browns: In a large bowl, combine the thawed hash browns, cheddar cheese, mozzarella cheese, and cooked sausage or bacon if using.
3. Mix Wet Ingredients: In another bowl, whisk together the sour cream, milk, eggs, garlic powder, onion powder, salt, and black pepper until well combined.
4. Combine Mixtures: Pour the wet mixture into the bowl with the hash brown mixture. Stir well until all ingredients are fully incorporated.
5. Transfer to Baking Dish: Spread the mixture evenly into the prepared baking dish.
6. Top It Off: Sprinkle additional cheese on top as desired for a golden-brown finish.
7. Bake: Place the dish in the preheated oven and bake for 45-50 minutes or until the casserole is set and the top is golden.
8. Cool: Remove the casserole from the oven and let it cool for about 5-10 minutes before serving.
9. Garnish (optional): Sprinkle chopped chives on top for added flavor and freshness.
10. Serve: Slice into squares and serve warm to enjoy the cheesy deliciousness!

By following these clear steps, you’ll create an incredible breakfast casserole that is sure to impress.