01 - Preheat oven to 375°F. Lightly grease a 9x13 inch baking dish with cooking spray or oil.
02 - In a large bowl, combine shredded chicken, 1 cup enchilada sauce, black beans, corn, red onion, cumin, chili powder, garlic powder, salt, and pepper. Mix thoroughly until all ingredients are evenly distributed.
03 - Spread 1/2 cup of enchilada sauce evenly across the bottom of the prepared baking dish to prevent sticking.
04 - Arrange four tortillas over the sauce, tearing as necessary to cover the bottom completely. Spread half the chicken mixture evenly over tortillas, then sprinkle with 2/3 cup shredded cheese.
05 - Add another layer of tortillas over the cheese. Top with remaining chicken mixture and another 2/3 cup cheese.
06 - Place final tortilla layer on top. Pour remaining 1/2 cup enchilada sauce evenly over surface. Top with remaining cheese and black olives if using.
07 - Cover baking dish tightly with aluminum foil. Bake for 20 minutes to heat through and meld flavors.
08 - Remove foil and bake uncovered for 10 additional minutes, or until cheese is bubbly and golden brown.
09 - Let casserole rest for 5 minutes before serving. Garnish with cilantro, green onions, avocado, and serve with sour cream and lime wedges.