Preheat oven to 350°F (175°C) and grease a 9x13-inch baking dish.
In a large mixing bowl, stir together sour cream, cream of chicken soup, melted butter, garlic powder, onion powder, salt, and pepper.
Fold in the thawed hash browns and shredded cheddar cheese. Mix until well combined.
Scoop the mixture into the prepared baking dish and spread it out evenly.
In a small bowl, toss the crushed cornflakes with 2 tablespoons melted butter, then sprinkle over the top.
Bake for 45–50 minutes until the top is golden and the edges are bubbling.
Let it cool for 5 minutes before serving (if you can wait that long).