Preheat your oven to 375°F and lightly grease a 9×13-inch baking dish.
In a skillet over medium heat, warm the olive oil and sauté the onion and garlic until they are softened, about 3 to 5 minutes.
Add the cooked, shredded chicken, cumin, chili powder, salt, and pepper to the skillet, stirring to combine.
Stir in the drained and rinsed black beans and 1 cup of enchilada sauce, then remove from heat.
Spread a thin layer of the remaining enchilada sauce on the bottom of the prepared baking dish.
Layer ⅓ of the tortilla pieces over the sauce, followed by ⅓ of the chicken and bean mixture, and ⅓ of the cheese. Repeat these layers two more times, ending with a layer of cheese on top.
Cover the casserole with foil and bake for 20 minutes.
Remove the foil and bake for an additional 20 minutes, or until the cheese is melted and bubbly.
Let the casserole rest for 5 minutes before serving.
