01 - Preheat oven to 350°F. Grease a 9x9-inch baking dish or similar casserole dish with butter or cooking spray.
02 - In a large bowl, add drained whole kernel corn, creamed corn, sour cream, melted butter, and Jiffy corn muffin mix. Stir with spatula until just blended—do not overmix.
03 - If incorporating cheese, fold shredded cheddar into batter until evenly distributed.
04 - Pour batter into prepared baking dish. Use spatula to spread mixture evenly across surface.
05 - Bake for 45–50 minutes until top is golden brown and center is set. A toothpick inserted in middle should come out clean or with moist crumbs.
06 - Remove from oven and let casserole rest for 5 minutes before serving. This allows texture to set for cleaner slicing.