Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the creamed corn, whole kernel corn (make sure it’s drained), sour cream, Jiffy corn muffin mix, and melted butter. Stir until all ingredients are well blended.
Transfer the mixture to a greased 9x13-inch baking dish or a 10-inch cast iron skillet, spreading it out evenly.
Bake, uncovered, for 45 minutes, or until the casserole is mostly set.
Sprinkle the shredded cheddar cheese over the top and return to the oven for an additional 10-15 minutes, or until the cheese is melted and begins to turn golden brown.
Allow the casserole to rest for 5 minutes before serving.