Preheat the oven to 350°F and spray a 9x13-inch baking dish with non-stick cooking spray.
In a large mixing bowl, combine 2 cups sour cream, 1 can (10.5 oz) cream of chicken soup, and ¼ cup melted unsalted butter (half of the ½ cup total butter). Stir until smooth and well combined.
Add 1 bag (32 oz) frozen diced hash browns, 2 cups shredded cheddar cheese, 1 teaspoon salt, and ¼ teaspoon black pepper. Stir until all ingredients are evenly combined.
Pour the potato mixture into the prepared 9x13-inch baking dish and spread it into an even layer.
Sprinkle 2 cups corn flakes evenly over the top of the casserole.
Drizzle the remaining ¼ cup melted unsalted butter over the corn flakes.
Bake for 45–50 minutes, or until the topping is golden brown and the potatoes are tender.
Remove the casserole from the oven and let it rest for 10–15 minutes before serving.
Serve warm and enjoy.
Notes
Refrigerate the leftovers in an airtight container for up to 5 days. You can use shredded hash browns instead of diced for this recipe if you prefer. This recipe can be made ahead. Make the casserole as detailed but do not add the cornflake topping. Cover and refrigerate for up to 24 hours. When baking, add the cornflake topping and bake per the recipe.