In a large bowl, combine the chicken, chiles, broth, soups and onion; set aside. Layer half of the tortillas in a greased 13x9-in. baking dish, cutting to fit pan if desired. Top with half of the chicken mixture and half of the cheese. Repeat layers. , Bake, uncovered, at 350° for 30 minutes or until heated through. Freeze option: Cover and freeze unbaked casserole. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake casserole as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165°. If desired, serve with sour cream and green onions.