Preheat oven to 350° . Lightly grease medium baking dish. Season chicken with garlic salt. Arrange in prepared baking dish. Bake 45 minutes in preheated oven, until no longer pink and juices run clear. Cool, shred, and set aside. With metal tongs, char each tortilla half over open flame of a gas stove burner for about 1 minute, until lightly puffed. *To skip the charring step, simply tear tortillas into fourths so they absorb sauce better. Pour about 1/2 inch enchilada sauce in bottom of medium baking dish, and arrange 6 tortillas in a single layer. Top with 1/2 the chicken, 1/3 cheese, 1/2 the sour cream, and 1/3 of the remaining enchilada sauce. Repeat. Coat remaining tortillas thoroughly with remaining enchilada sauce, and arrange on top of the layers. Sprinkle with remaining cheese, and top with any remaining enchilada sauce. Cover, and bake 45 minutes in the preheated oven. Cool slightly before serving.