Preheat the oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish.
In a large bowl, combine the shredded chicken, black beans, corn, diced tomatoes with green chiles, taco seasoning, salsa, sour cream, and 1 cup of the shredded cheese. Mix until well combined.
Spread half of the tortilla pieces evenly in the prepared baking dish.
Spoon the chicken mixture over the tortillas and spread into an even layer.
Top with the remaining tortilla pieces and sprinkle with the remaining 1 cup of shredded cheese.
Cover the dish with foil and bake for 20 minutes.
Remove the foil and bake for another 10 to 15 minutes, or until the cheese is melted and bubbly.
Let the casserole rest for 10 minutes.
Garnish with the sliced green onions and fresh cilantro.
Serve with your favorite taco toppings if desired.