Sauté onions & chilies in olive oil. Combine enchilada sauce, chicken soup, evaporated milk, and chicken broth until smooth. Add onions and chilies and set aside.
Stir together cream cheese, 1½ cups shredded cheddar cheese, black olives, onion, and chopped chicken. It should be thick.
Tear tortillas into pieces. Spray 9” x 13” casserole baking dish with Pam (or similar.) Add ½ cup of sauce to bottom of the pan. Layer tortilla pieces in dish with spoonfuls of chicken mixture, ½ C sauce, and half of remaining cheese. Do this twice, ending with cheese. Pour remainder of sauce over all. Cover and refrigerate several hours or overnight. Bake uncovered at 350° for 1 hour.