1Heat oven to 400°F. Line baking sheet with foil; spray with cooking spray. Between pieces of plastic wrap or waxed paper, place each chicken breast smooth side down; gently pound with flat side of meat mallet or rolling pin until about 1/2-inch thick.
2In shallow dish, mix together maple syrup and mayonnaise. In another shallow dish, mix together panko and pecans. Dip chicken into syrup mixture, then into panko. Place on baking sheet. Spray top of chicken with cooking spray.
3Bake 15 to 20 minutes, turning once, until juice of chicken is clear when center of thickest part is cut (165°F) and coating is golden brown.