Making your White Chicken Enchilada Casserole is effortless when you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Prepare the Filling: In a large bowl, mix together the shredded chicken, diced green chilies, cream of chicken soup, sour cream, half of the Monterey Jack cheese, diced onion, garlic powder, cumin, chili powder, salt, and pepper.
3. Prepare the Tortillas: If preferred, lightly warm the corn tortillas in the microwave to make them pliable.
4. Layer the Casserole: Spread a thin layer of the chicken mixture at the bottom of a 9×13 inch baking dish.
5. Add Tortillas: Layer 4 corn tortillas over the chicken mixture, overlapping them slightly.
6. Add More Filling: Spoon half of the remaining chicken mixture over the tortillas and spread evenly.
7. Repeat Layers: Add another layer of 4 tortillas over the filling, followed by the rest of the chicken mixture.
8. Finish with Tortillas: Arrange the last 4 tortillas on top, finishing the assembly.
9. Add Cheese: Sprinkle the remaining Monterey Jack cheese and cheddar cheese evenly over the top layer of tortillas.
10. Bake the Casserole: Cover with aluminum foil and bake in the preheated oven for 20 minutes. Then remove the foil and bake for an additional 10 minutes or until the cheese is bubbly and golden brown.
11. Cool Before Serving: Allow the casserole to cool slightly for 5-10 minutes to set before slicing into portions.

Following these clear instructions will lead you to prepare an irresistible casserole that everyone will love!