Combine the first 7 ingredients in a bowl, and stir well.
Place the chicken in a shallow dish; spread 1/2 cup pesto mixture over both sides of chicken. Cover and marinate in refrigerator for 1 to 4 hours.
Prepare grill. Place chicken breast halves, bone side up, on grill rack coated with cooking spray, and grill for 40 minutes or until the chicken is done, turning occasionally and basting with the remaining 1/4 cup of pesto mixture. Garnish with sage sprigs, if desired.