1. Place chickens in a large, nonreactive (glass) bowl.
2. Combine remaining ingredients in a blender and process to a smooth puree. Pour half this sauce over the chicken parts, coating them well. Refrigerate remaining sauce, bringing it to room temperature before serving time. Cover and let chicken marinate in the refrigerator for 4-12 hours (the longer the better).
3. Cook on gas grill on medium.
4. When ready to cook, oil the grill grate. Place the chickens, skin side up, on the hot grate, reserving any marinade in the bowl. Brush chickens with the marinade, then cover the grill and cook for 30 minutes. Uncover and brush chickens with marinade. Cover and continue grilling until juices run clear from thickest part of thigh or until an instant-read meat thermometer inserted in thigh registers 180 degrees. For crisp skin, place the chickens skin side down on the grate directly over the fire for the last 5-10 minutes.
5. Using spatulas, carefully transfer chicken to a platter. Serve with reserved sauce.

