Preheat the oven to 350˚F.
In a large casserole dish, add the melted butter, Jiffy mix, corn, creamed corn, egg, and half of the cheddar cheese (about 1 cup.) Mix until everything is combined.
Dollop the sour cream evenly over the top, then use a knife to gently swirl it into the casserole. Sprinkle the remaining cheese over the top.
Bake on the middle rack in the oven for 40-45 minutes or until the middle is set (cooked through.) Remove from the oven and serve warm.