Preheat your oven to 350°F. Lightly grease an 8x8-inch baking dish with nonstick spray and set it aside.
In a large mixing bowl, whisk the eggs until just combined. Add the melted butter and whisk again until smooth.
Stir in the sour cream, corn muffin mix, cream-style corn, and whole kernel corn until just combined. Avoid over mixing for the best texture.
Pour the batter into the prepared baking dish, spreading it evenly.
Bake for 50-55 minutes, or until the edges are golden brown and the center is set. The middle may have a slight jiggle but should not be overly wobbly.
Let it cool for a few minutes before serving.
Video
Notes
Tips
Let the filled casserole dish sit at room temperature while the oven preheats so it warms up gradually and avoids cracking.
Do not drain the can of regular corn; the extra moisture helps keep the casserole soft and custardy.
Mix the batter just until combined to keep the texture tender.
Storage & Make Ahead
Cover and refrigerate leftovers for up to 4 days.
Prepare the casserole up to 24 hours ahead, cover tightly, and refrigerate; let it warm at room temperature while the oven preheats before baking.
Reheat leftovers covered with foil at 325°F for about 20 minutes or until warmed through.