Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, black beans, corn, enchilada sauce, salsa, 1 cup of shredded cheese, cumin, salt, and black pepper. Mix until well combined.
Spread the chicken mixture evenly in the bottom of a greased 9x13 inch baking dish.
In a separate bowl, prepare the cornbread mix according to the package instructions. Stir in the egg and milk until fully incorporated.
Pour the cornbread batter evenly over the chicken mixture in the baking dish.
Bake in the preheated oven for 30 minutes, or until the cornbread is golden brown and cooked through.
Remove from the oven and sprinkle the remaining 1 cup of shredded cheese on top. Return to the oven for an additional 10 minutes, until the cheese is melted and bubbly.
Let the casserole cool for a few minutes before serving. Top with optional sour cream, green onions, or cilantro if desired.