HEAT oven to 400ºF.
ADD hot water to stuffing mix in large bowl; stir just until moistened. Stir in onions and parsley. Let stand 5 min. Meanwhile, make lengthwise cut in thick side of each chicken breast, being careful to not cut through to opposite side. Open breasts; place, top-sides down, between sheets of waxed paper. Pound to 1/4-inch thickness.
STIR cranberries and nuts into stuffing; spread 1/2 cup onto half of each breast. Fold in half to enclose filling. Secure with wooden toothpicks, if desired. Place in 13x9-inch baking dish; brush with dressing.
BAKE 30 to 35 min. or until chicken is done (170ºF).