Preheat the Oven: Heat the oven to 350°F. Lightly grease a suitable casserole baking dish.
Prepare the Corn: Drain the whole-kernel corn thoroughly. Keep the cream-style corn undrained for the creamy texture.
Mix the Ingredients: In a large mixing bowl, combine both types of corn, corn muffin mix, sour cream, and melted butter. Stir until evenly combined.
Fill the Baking Dish: Transfer the mixture to the prepared dish and spread it into an even layer.
Bake Until Set: Bake for 40–45 minutes, or until the top looks golden and the center is mostly set.
Add the Cheese: Sprinkle shredded cheddar cheese over the casserole.
Melt the Topping: Return the dish to the oven for about 5 minutes, until the cheese melts.
Rest and Serve: Let the casserole rest for 5–10 minutes before serving so it can settle and is easier to scoop.