Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with cooking spray or butter.
In a large mixing bowl, combine the thawed hash browns, sour cream, cream of chicken soup, French onion dip, 1 1/2 cups of cheddar cheese, garlic powder, onion powder, salt, and black pepper. Mix until well combined.
Spread the mixture evenly into the prepared baking dish.
In a separate bowl, combine the crushed cornflakes with the melted butter. Stir until the cornflakes are evenly coated.
Sprinkle the cornflake mixture over the top of the potato mixture in the baking dish.
Bake in the preheated oven for 45-50 minutes, or until the top is golden brown and the edges are bubbling.
Remove from the oven and let it cool for about 10 minutes before serving. Top with the remaining 1/2 cup of cheddar cheese, if desired, and allow it to melt slightly before serving.