Wrap each breast half in slice of bacon. Arrange beef in a thin layer in bottom of 9 x 13 inch baking dish. Place chicken on beef. Saute mushrooms in butter.
Prepare white sauce: Melt 3 tablespoons butter over low heat in saucepan. Blend 3 tablespoons flour, 3/8 teaspoon salt and 1/8 teaspoon pepper. Cook over low heat, stirring until mixture is smooth and bubbly. Remove from heat. Stir in 1 1/2 cup milk. Bring to a boil, stirring constantly. Boil 1 minute.
Fold mushrooms and sour cream into white sauce. Pour sauce over chicken. Bake at 350 degrees for 1 1/2 hours. Serve on beds of rice. 8 servings
