Gather all ingredients and preheat the oven to 350 degrees F (175 degrees C).
Combine hash browns, Cheddar cheese, condensed soup, sour cream, ½ cup melted butter, onion, salt, and pepper in a large bowl.
Transfer mixture to a 3-quart casserole dish.
Add remaining 1/4 cup melted butter and cornflakes to a saucepan over medium heat; stir gently until cornflakes are coated in butter.
Sprinkle cornflake mixture on top of casserole.
Cover casserole and bake in the preheated oven until hot and top is crispy, about 40 minutes.
Serve warm and enjoy!