CHOP enough mango to measure 1/3 cup; place in blender. Add dressing; blend until smooth. Pour 1/4 cup over chicken in shallow glass dish; turn chicken over to coat both sides of each breast. Refrigerate 30 min. to marinate.
REMOVE chicken from marinade; discard marinade. Cook chicken in nonstick skillet sprayed with cooking spray on medium-high heat 5 min. on each side or until done (165ºF). Cool slightly. Slice chicken; chop remaining mango.
TOSS spinach with strawberries, chopped mangos, onions and 1/4 cup of the remaining dressing mixture; spoon onto 4 plates. Fan 1 chicken breast over each salad. Top with remaining dressing mixture and nuts.