Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with cooking spray or a little bit of oil.
Prepare the Chicken Mixture: In a large bowl, mix the shredded chicken with half of the enchilada sauce, diced green chiles, cumin, salt, and pepper. Set aside.
Layer the Casserole:
First Layer: Spread a small amount of enchilada sauce on the bottom of the prepared baking dish. Arrange a layer of cut tortillas over the sauce, covering the bottom of the dish.
Second Layer: Spread half of the chicken mixture over the tortillas. Top with half of the black beans, corn, and diced onion. Sprinkle a third of the cheese over the top.
Third Layer: Add another layer of cut tortillas, followed by the remaining chicken mixture, black beans, corn, and onion. Sprinkle another third of the cheese over the top.
Fourth Layer: Finish with a final layer of cut tortillas. Pour the remaining enchilada sauce evenly over the top, ensuring all the tortillas are covered. Sprinkle the remaining cheese over the sauce.
Bake: Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and slightly golden.
Cool and Serve: Let the casserole cool for about 10 minutes before serving. This helps the layers set, making it easier to cut and serve.
Garnish and Enjoy: Serve with optional garnishes like sour cream, chopped fresh cilantro, diced avocado, sliced jalapeños, and lime wedges on the side.
