Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish. In a large bowl, mix shredded chicken with taco seasoning, salsa, and Rotel until well coated.
Stir in the black beans, corn (if using), and sour cream. Mix everything until well combined and creamy.
Spread a layer of tortilla pieces on the bottom of the prepared dish. Top with half of the chicken mixture and a generous sprinkle of cheese. Repeat the layers with the remaining tortillas, chicken mixture, and cheese.
Cover the dish with foil and bake for 20 minutes. Remove the foil and bake an additional 5–10 minutes, or until the cheese is bubbly and slightly golden.
Let the casserole rest for 5 minutes before serving. Garnish with chopped cilantro, green onions, or jalapeños if desired. Serve with extra sour cream, salsa, or avocado on the side.