Beat egg in a small bowl, then pour egg beat into a shallow dish or bowl and blend in sour cream. Crush graham crackers into crumbs and, in a separate shallow dish or bowl, combine rosemary, bread crumbs and crushed graham cracker crumbs.
Lightly coat chicken with flour; dip floured chicken breasts in egg mixture, then crumb mixture and place in a lightly greased 9x13 inch baking dish.
Bake at 350 degrees F (175 degrees C) for 1 hour or until chicken is cooked through and juices run clear.
