01 - Preheat the oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 - In a medium skillet over medium heat, sauté the chopped onion for 3–4 minutes until softened. Add minced garlic and cook for an additional minute.
03 - In a large mixing bowl, combine shredded chicken, sautéed onion and garlic, black beans, corn, and 1/2 cup of enchilada sauce. Mix thoroughly.
04 - Spread 1/2 cup of enchilada sauce evenly on the bottom of the prepared baking dish.
05 - Arrange half of the tortillas over the sauce, overlapping as needed.
06 - Spread half of the chicken mixture evenly over the tortillas. Sprinkle with 1 cup shredded cheddar and 1/2 cup Monterey Jack cheese.
07 - Repeat with remaining tortillas, chicken mixture, and cheeses, layering evenly.
08 - Pour the remaining enchilada sauce evenly over the layered casserole.
09 - Cover the dish with foil and bake for 25 minutes.
10 - Remove foil and bake for an additional 10 minutes until cheese is bubbly and golden.
11 - Allow the casserole to rest for 10 minutes before garnishing with cilantro, green onions, and serving with sour cream and lime wedges.