Preheat the oven to 350°F. Spray a 9x9-inch (or 2 1/2 quart) baking dish with nonstick cooking spray.
In a bowl, mix together the 7 ounce packet of cornbread mix, ½ cup of milk, and 1 large egg until well combined.
Pour the cornbread batter into the prepared baking dish and bake for about 15 minutes.
While the cornbread is baking, cook and crumble 1 pound of ground beef in a skillet until it is no longer pink, then drain any excess grease.
Add 3 Tablespoons of taco seasoning and 1/3 cup of water to the cooked beef, and stir to mix well.
Stir in the drained 11 ounce can of Mexicorn and the drained 10 ounce can of Rotel, and let the mixture simmer for a couple of minutes.
Once the cornbread has finished baking, remove it from the oven and layer the ground beef mixture on top.
In a separate bowl, combine 2 cups of sour cream with 1 cup of the shredded Mexican cheese blend and ½ cup of chopped green onions.
Carefully spread the sour cream mixture over the ground beef layer.
Top everything with the remaining 1 cup of shredded Mexican cheese blend.
Bake the dish uncovered for about 25 minutes, or until it is heated through and the cheese is melted.
Allow the bake to cool for a few minutes before slicing and serving with optional toppings like shredded lettuce, sliced olives, diced tomatoes, and taco sauce.
