Preheat oven to 400 degrees F. While the oven is preheating, season both sides of chicken breasts with salt, pepper and paprika. Add olive oil to a large skillet and heat over medium heat. Place chicken in the heated skillet and cook chicken 5 minutes per side or until internal temperature reaches 165 degrees F.
While the chicken is cooking, chop your peppers (be sure to remove the seeds and ribs from inside), and onion. Once the chicken is cooked on both sides, remove the chicken from the pan and set aside.
In the same pan you cooked the chicken in, add butter then all your chopped veggies and cook over medium heat until soft, about 7 minutes stirring occasionally. While the veggies are cooking, chop the cooked chicken into small pieces or shred.
Once the veggies are soft add in the flour and stir until dissolved. Next, add chicken broth to create the creamy gravy. When the gravy is thickened add in cumin, chili powder and cayenne pepper (optional) and adjust to taste.
Drain the juice from the canned diced tomatoes and green chilies. Now, combine the gravy, chopped cooked chicken, sour cream, diced tomatoes and green chilies, cream cheese and cheddar cheese then stir to combine. The mix will be thick.
In a 13x9 inch pan spread a thin layer of the chicken gravy mixture then put torn tortillas over the top. Repeat this layering of gravy and tortillas three times then top with Mexican shredded cheese. Bake for 25-30 minutes on the center rack until bubbling and enjoy topped with green onion, cilantro or avocado. Enjoy!
Leftover Storage: Store leftover King Ranch Chicken in an airtight container in the fridge for up to 4 days. Tortilla Options: You can use either flour or corn tortillas for this casserole. Personally, I enjoy flour but either work great. Spice Option: To make the chicken casserole spicier you can add in some cayenne pepper, red pepper flakes or diced jalapeno pepper.