Preheat oven to 350F (180C). Spray a 1 ½ -quart baking dish (or an 8-inch square dish) with nonstick spray.
In a large bowl, toss together chicken, half of the taco sauce (about ½ cup) and half of the cheese (about ½ cup).
Place 2 of the tortillas in the bottom of the prepared dish, tearing them as necessary to cover the bottom (overlapping is fine).
Top with half of the chicken mixture and drizzle with ¼ cup of remaining taco 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!
Cooking for Two? The portions are small in this dish, so you might prefer to prepare the whole recipe and just enjoy a larger serving. In the alternative, you can use a smaller baking dish and cut the ingredients in half (just tear the tortillas to fit the size/shape of any dish that you are using).Want to Prep Ahead? This is a great freezer meal to make in advance. Follow the recipe instructions through Step 4, then wrap tightly with plastic wrap and foil. Freeze for up to 3 months. When ready to bake, you can thaw in the refrigerator overnight and bake as instructed; OR you can bake the frozen casserole (just add about 15 minutes to the baking time, or cook until completely heated through).