Preheat oven to 180 C / Gas mark 4. Lightly grease a medium baking dish.
Season chicken with salt. Arrange in the prepared baking dish. Bake 45 minutes in the preheated oven, until no longer pink and juices run clear. Cool, shred and set aside.
Pour enchilada sauce to cover 1 to 2cm of the bottom of the prepared baking dish, and arrange 4 tortillas in a single layer. Top with 1/2 the chicken, 1/3 cheese, 1/2 the soured 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.