Irresistible Southern-Style Cornbread Casserole

Preheat Oven: Preheat your oven to $175^\circ\text{C}$ ( $350^\circ\text{F}$ ).
Prepare Dish: Lightly grease a 9×13 inch (or similarly sized) baking dish. The rectangular shape in the image is typically 9×13.

Combine: In a large mixing bowl, whisk together the melted butter and the lightly beaten egg until well combined.
Add Dairy: Stir in the sour cream (or Greek yogurt) until the mixture is smooth.

Add Corn: Gently stir in both the drained whole kernel corn and the undrained cream-style corn.
Add Mix: Pour in the cornbread mix (or the homemade cornmeal/flour mixture). Stir just until the dry ingredients are fully moistened and there are no large pockets of dry mix. Do not overmix; overmixing will develop the gluten and result in a tough, less tender casserole.
Season and Cheese: Stir in the salt, pepper, and shredded cheddar cheese (if using).

Transfer: Pour the batter into the prepared baking dish, smoothing the top with a spatula.
Initial Bake: Bake for 35 minutes. At this point, the casserole should be mostly set but still slightly moist in the center.

Butter Brush: After the initial 35 minutes, remove the casserole from the oven. Brush the entire top surface lightly with the extra 1 tablespoon of melted butter.
Sprinkle: Sprinkle the top evenly with the chopped fresh thyme/chives and panko breadcrumbs (if using). This creates the delightful, golden, and herby crust seen in the photograph.
Final Bake: Return the casserole to the oven and continue baking for another 10-15 minutes, or until the topping is a deep golden brown, the edges are pulling away from the dish, and a toothpick inserted into the center comes out mostly clean (a few moist crumbs are fine).

Rest: Let the casserole rest for 5-10 minutes after removing it from the oven to allow it to set further.
Serve: Serve warm as a hearty side dish for grilled meats, BBQ, Thanksgiving, or holiday dinners.