In a large bowl, combine the thawed hash browns, melted butter, cream of chicken soup, sour cream, chopped onion, shredded cheddar cheese, salt, and black pepper.
Spread the mixture evenly into a 9x13 inch baking dish.
In a small bowl, combine the crushed cornflakes with the melted butter for topping.
Sprinkle the buttered cornflakes evenly over the potato mixture.
Bake in the preheated oven for 45 minutes or until bubbly and golden brown on top.
Notes
This cheesy potato casserole is a great side dish option for brunches, potlucks, or holiday meals.