Clean and rinse the chicken; then open it completely, cutting through the breastbone with a suitable pair of scissors. Flatten it out on a chopping board by pressing down hard with open hands, or maybe with the use of a meat mallet. Peel the cloves of garlic and rub them all over the skin. Put the chicken in a bowl or serving dish and season it with the olive oil, lemon juice, pepper and some salt, beaten together with a fork. Now add the sprigs of rosemary, broken into pieces, and a sprinkling of salt on both sides. It’s best to season the chicken at least an hour before cooking it, and to turn it over in its marinade of lemon and oil at least twice. Lay the chicken on a grill (1) or in a heavy-bottomed, non-stick frying pan, with the outside facing upwards, trying to flatten it as much as possible. Cook it over a very low heat for about half an hour (keeping it covered with a heavy lid, to make sure it’s pressed down, for the first 10 minutes). Turn the chicken, which should be browned but not burnt, and cook it on the other side for about half an hour as well. Take it off the grill and drizzle 1 or 2 spoonfuls of the marinade (previously set aside) over it on both sides. Cut it into 2 or 4 pieces (according to how many people are going to eat it, and their appetites) and serve immediately, while nice and hot. It’s a really delicious dish, and very Tuscan!
(1) The ideal thing for cooking “alla diavola” is a fireplace or barbeque, where you can prepare good embers.