Preheat oven to 350°F (180°C). Grease a 2-quart baking dish.
Spread ¼ cup of the enchilada sauce in a thin layer in the bottom of the dish.
In a large bowl, stir together the chicken, ¾ cup of the enchilada sauce, and about half of the cheese (½ cup).
Place 4 of the tortillas in the bottom of the prepared dish, tearing or overlapping them as necessary to cover the bottom.
Top with half of the chicken mixture and drizzle with ¼ cup of enchilada sauce. Repeat layers one more time.
Cover with foil and bake for 30 minutes. Uncover, sprinkle with remaining ½ cup of cheese, and bake for an additional 5-10 minutes (until cheese melted and casserole is hot and bubbly).
Garnish with optional toppings and serve.
