Preheat the oven to 350°F and grease a baking dish or skillet to prevent sticking.
In a large bowl, combine the creamed corn, drained whole kernel corn, corn muffin mix, sour cream, and melted butter. Mix until everything is evenly incorporated and the batter looks smooth and thick.
Pour the mixture into the prepared baking dish and spread it out evenly so it cooks uniformly.
Place the dish in the oven and bake uncovered until the casserole begins to set and lightly firm up.
Remove the dish briefly, sprinkle the shredded cheddar cheese evenly over the top, and return it to the oven.
Continue baking until the cheese melts and the top develops a light golden color.
Allow the casserole to rest for a few minutes before serving so it can firm up slightly and be easier to scoop.