Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with cooking spray or a little olive oil to prevent sticking.
Prepare the chicken:
If you haven’t already, cook and shred the chicken. You can either poach the chicken in water or chicken broth for 15-20 minutes until cooked through and tender, or use a rotisserie chicken for convenience.
Make the sauce mixture:
In a medium bowl, combine the enchilada sauce, cream of chicken soup, and sour cream. Stir in the garlic powder, cumin, chili powder, and a pinch of salt and pepper. If using, also add the green chilies and the chopped onion. Mix well to combine.
Assemble the casserole:
Spread a thin layer of the sour cream sauce mixture on the bottom of the prepared baking dish.
Layer half of the tortilla strips (or chips) over the sauce.
Spread half of the shredded chicken over the tortillas.
Pour half of the remaining sour cream mixture over the chicken, and sprinkle with 1 cup of shredded cheese.
Repeat with another layer of tortillas, chicken, sauce, and the remaining 1 cup of cheese.
Bake the casserole:
Cover the casserole with aluminum foil and bake for 20 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly and the casserole is heated through.
Garnish and serve:
Once the casserole is done, remove it from the oven and let it sit for 5-10 minutes before serving.
Garnish with freshly chopped cilantro or green onions for an added burst of flavor and color.
Serve with a side of Mexican rice, beans, or a fresh salad for a complete meal.
