In a wide shallow pan or large deep skillet, combine all ingredients except the duck. Bring to a boil, then reduce heat to low and simmer five minutes. Meanwhile, rinse the duck; remove giblets and neck, reserving for soup. Truss the duck, making a handle of the string. Place the pan with the hot soy mixture in the sink. Holding the duck by the handle over the pan, ladle hot soy mixture on all sides until the skin has a "cooked" look. Hang duck in a cool, airy, breezy place for 4 to 6 hours to dry the skin. Or, place duck on a wire rack over a pan and refrigerate overnight. Pour leftover mixture in an oven-proof saucepan. Place duck, breast side down, in a roast holder inside a deep aluminum foil drip pan. Place pan in the center of grill; cover and grill for 1- half to 1- 0.75 hours using over deep drip pan containing 1 cm water. Place soy mixture over direct coals and boil to reduce by half. Strain soy mixture through a fine sieve and serve with duckling.