Preheat oven to 375 degrees. In a greased 13 x 9 baking dish, layer half of each of the following: chicken, enchilada sauce, sour cream, tortillas and cheese. Repeat layers.
Bake covered 40 minutes. Uncover; bake until bubbly, about 10 minutes. Let stand 15 minutes before serving.
Freeze Option: Cover and freeze unbaked casserole. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 375 degrees. Bake casserole as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165 degrees.