Preheat oven to 350 degrees F. Grease a 9x13-inch casserole dish; set aside.
In a large bowl, use a rubber spatula to mix together the corn, muffin mix, sour cream, melted butter, and 1 cup of the cheese. Pour the mixture into the prepared casserole dish and spread into an even layer.
Bake for 45 to 55 minutes, or until the top is golden brown and a toothpick inserted in the center comes out with moist crumbs attached. Increase the oven temperature to 400 degrees F and sprinkle the top with the remaining cheddar cheese. Return to the oven and bake for an additional 5 to 10 minutes, until the cheese is melted and bubbly. Allow the casserole to sit for at least 5 minutes before serving. Leftovers can be stored in an airtight container in the refrigerator for up to 4 days.