Preheat oven to 375°F (190°C). Lightly grease a 9x9-inch baking dish.
Stir chicken, enchilada sauce, beans, corn, sour cream, chili powder, cumin, salt, and pepper in a bowl until combined.
Layer a third of the tortilla quarters in the bottom of the dish. Spoon half the chicken mixture over them and sprinkle with a third of the cheese.
Repeat another layer of tortillas, the remaining chicken mix, and cheese. Finish with final tortilla pieces and remaining cheese.
Bake uncovered 20–25 minutes until bubbly and cheese is melted. Let rest 5 minutes before serving. Top with green onions, cilantro, or avocado if using.