Preheat the oven to 350°F. Lightly spray a 9×11 casserole dish with nonstick cooking spray.
In a small bowl, melt ½ cup salted butter in the microwave for 20-40 seconds, or until fully melted. Let the butter cool while preparing other ingredients.
In a large bowl, add the 8 ½ oz Jiffy Corn Muffin Mix, 15 oz canned whole kernel corn (drained), 15 oz canned creamed corn, and 1 cup sour cream. Check the butter to see if it’s cooled enough. Once it has, add the melted salted butter as well. Mix everything together.
Pour the mixture into the prepared baking dish. Spread it out evenly with a spatula. Place in the oven to bake for 60-70 minutes, or until the edges are golden brown. Scoop onto plates to serve while still warm.