Squeeze cooled garlic cloves out of the head into a small chopper or food processor. Add remaining ingredients. Blend until herbs are finely chopped and a sauce forms. 

Loosen skin from chicken thighs, and spoon herb sauce under the skin. Rub more sauce all over the outside of the thigh, and transfer to a bowl. Repeat with remaining meat. Cover and transfer to a fridge for a minimum of one hour, or overnight.

Remove chicken from fridge and allow to rest at room temperature for 30 minutes. Heat a BBQ to 400°. Spritz grill with olive oil or cooking spray, then carefully add meat, skin side down, to the hot grill (all that olive oil can create big flames, so shake off excess oil/sauce before placing on the grill). Grill for approximately 10 minutes until the skin is well crisped and dark in colour.

Reduce heat to 300° and flip chicken pieces skin-side up, positioning them in indirect heat (turn a zone in the BBQ way down or off, placing chicken into that zone). Cook over lower heat for another 20 minutes or so, until the meat is cooked through. (Temperature should be 165°—I press down on the chicken with my tongs to get a sense of the firmness to see how cooked they are. Firmer meat means more cooked).

During the last seven or so minutes, mist the peach halves with olive oil and place on the grill, starting skin side up. Get some nice grill lines, then filp and finish cooking the peaches until juices are flowing and the fruit has softened.

Serve the chicken and peaches together on a platter.