Preheat Oven: Heat the oven to 200C/gas 6/fan 180C. Loosen the chicken breast skin and insert slices of prosciutto and a sprig of rosemary under it.
Prepare Chicken: Place the remaining prosciutto, onion, and herbs in the chicken cavity. Secure with cocktail sticks and set in a roasting pan.
Roast Chicken: Drizzle olive oil over the chicken, season, and roast for 1 hour 15 minutes, basting with wine periodically until cooked.
Prepare Sauce: Blend garlic, parsley, livers, anchovies, and optional salami in a food processor until smooth.
Cook Sauce: In a saucepan, combine the olive oil from the roasting pan with the liver mixture. Cook while stirring and add lemon juice, wine, and vinegar.
Finish Sauce: Return the blended sauce to the saucepan and continue cooking until it reaches a velvety consistency. Season with parsley and lemon zest.
Serve: Carve the chicken, discard used seasonings, and serve with the prepared sauce.