How to Make It
Set the chicken skin side up on a large rimmed baking sheet. Flatten the bird, fold the wing tips under the wingettes, point the drumsticks out and arrange the thighs next to the breasts. In a bowl, mix the garlic, rosemary, lemon zest, crushed red pepper, salt and black pepper with the 3 tablespoons of olive oil. Turn the chicken over and rub one-fourth of the marinade on the meat. Turn the chicken skin side up and rub the remaining marinade over the skin. Cover with plastic wrap and refrigerate overnight or for up to 24 hours.
In a small bowl, combine the minced shallot and vinegar and let stand for 10 minutes. In a food processor, combine the parsley, mint, garlic, anchovies and capers and process until finely chopped. Add the shallot-and-vinegar mixture. With the machine on, slowly pour in the olive oil until incorporated. Season with salt.
Light a charcoal fire. When the coals are hot, push them to one side of the grill. Brush the side of the grill opposite the coals with oil. Set the chicken on the oiled side of the grill, skin side down. Cover and grill for about 25 minutes, or until lightly charred on the bottom. Turn the chicken, cover and grill for about 20 minutes longer, or until cooked through. Transfer the chicken to a carving board and let rest for 10 minutes before carving.
Spoon the Sage Polenta onto warm plates. Arrange the chicken alongside and serve with the salsa verde.