Preheat oven to 375º F. Spray a 13x9 inch baking dish with non stick spray. Set aside.
In a skillet heat oil to medium high heat. Add onions and cook for 4-5 minutes until they are soft and translucent. If using peppers you can add them here as well.
1 Tablespoon oil, ½ onion
In a large bowl mix together chicken, with the onions, and everything else but the tortillas and cheese. Mix until well combined.
3 cups cooked and shredded chicken, 1 can cream of chicken soup, 1 can cream of mushroom soup, 1 can diced tomatoes with green chiles, 1 teaspoon chili powder, 1 teaspoon cumin, ¼ teaspoon black pepper
In the bottom of the prepared baking dish arrange a layer of tortilla pieces. Top with 1/3 of the chicken mixture, and sprinkle over 1/3 of the shredded cheese. Repeat with 2 more layers ending with shredded cheese on top.
12 corn tortillas, 2 cups shredded cheddar cheese
Place in the oven and bake for 30-40 minutes until bubbly and hot. Remove and let set for 5 minutes before serving.
Notes
Options – Bell pepper or poblano pepper are common additions.
I like to cut the tortillas to make the casserole easier to serve. You can leave them whole if you like.
I seasoned the chicken breasts with chicken seasoning and cooked them in the Instant Pot with ½ cup of water for 15 minutes. Afterward, I used two forks to shred them.