Place each chicken breast between 2 sheets of cling film or baking parchment. Use a meat mallet or rolling pin to
bash each piece of chicken – flatten out to an even layer about 0.5cm thick. Transfer to a dish.
To make the marinade, crush the garlic with a good pinch of salt using a pestle and mortar. Add the rosemary and sage, and give everything a good pounding. Stir through the lemon zest and juice, olive oil and some ground black pepper. Pour the marinade over the chicken, ensuring that it’s well coated. Cover and chill for at least 2 hrs.
Heat the barbecue. Once the flames have died down, spread the coals out to an even layer. Cook the chicken for 1-2 mins each side. Transfer to a board and leave to rest for a few mins.
Meanwhile, pour the oil and balsamic vinegar into a large bowl. Add the rocket and some seasoning. Toss together, then shave over the Parmesan. Serve the salad with the chicken, with lemon wedges to squeeze over.