Place chicken breasts in a 9x13 inch baking dish. In a small bowl combine the ginger, soy sauce, onion flakes, sugar, bourbon and garlic powder. Mix together and pour mixture over chicken. Cover dish and place in refrigerator. Marinate overnight.
Preheat oven to 325 degrees F (165 degrees C).
Remove dish from refrigerator and remove cover. Bake in the preheated oven, basting frequently, for 1 1/2 hours or until chicken is well browned and juices run clear.