Place first 3 ingredients in a food processor; process until finely chopped. Add yogurt and the next 8 ingredients (yogurt through nutmeg); pulse 4 times or until blended.
Make 3 diagonal cuts 1/4 inch deep across top of each chicken breast half. Combine chicken and yogurt mixture in a large zip-top plastic bag. Seal and marinate in refrigerator 8 hours or overnight, turning occasionally.
Prepare grill or broiler.
Remove chicken breast from bag; discard marinade. Place chicken on grill rack or broiler pan coated with cooking spray; cook 6 minutes on each side or until chicken is done.