Preheat your oven to 350°F (175°C).
In a large bowl, combine shredded chicken, cream of mushroom soup, diced tomatoes and chilies, sour cream, and seasonings.
Add diced onions and half of the shredded cheese to the mixture, then stir in the tortilla strips.
Layer half of the mixture in a greased 9x13 inch baking dish.
Sprinkle half of the remaining cheese over the first layer, then add the rest of the chicken mixture on top.
Top with the remaining cheese and cover the dish with foil.
Bake for 30-40 minutes, or until heated through and bubbly.
Remove the foil and bake for an additional 10 minutes to allow the cheese to brown.
Let the casserole sit for 10 minutes before serving.