Preheat the oven: Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch casserole dish with cooking spray or butter.
Mix the base: In a large mixing bowl, combine the melted butter, cream-style corn, whole kernel corn, and sour cream. Stir until fully incorporated.
Add cornbread mix and cheese: Fold in the Jiffy cornbread mix and stir until smooth. If using cheese, gently fold it into the batter.
Bake: Pour the mixture evenly into the prepared casserole dish. Bake for about 40 minutes, or until the center is set and a toothpick inserted in the middle comes out clean.
Serve: Let cool slightly, then serve warm for the best creamy texture and flavor.