1. Using a large knife, cut the backbones from the chickens and flatten each bird with the palm of your hand. Place each chicken in its own re-sealable plastic bag. Divide the rosemary, chilli flakes, garlic, lemon juice, lemon quarters, and olive oil between each bag, then seal them and turn a few times to coat evenly. Leave in the refrigerator overnight, turning the bags from time to time.

2. Remove the chickens from the fridge 2 hours before cooking to allow them to come to room temperature.

3. Preheat a grill to high; if using charcoal, let the coals burn until covered with white ash.

4. Remove the chickens from the bags and season both sides with salt and pepper. Put the chickens on the grill skin-side down and cook, turning every 10 to 12 minutes and brushing regularly with a sprig of rosemary dipped in olive oil. Continue until the chicken is cooked through and the juices run clear when pierced to the bone, about 40 minutes.

5. Remove from the grill and rest in a warm oven for 10 minutes. Once rested, cut each bird in half and place each half on a plate. Drizzle with extra virgin olive oil.