Preheat oven to 200°C (390°F). Combine the butter and pepper in a bowl. Carefully loosen the chicken skin with your fingers and place ¾ of the butter mixture and the sage under the skin. Place the lemon in the chicken cavity and secure the legs with kitchen string. Rub the remaining butter mixture over the chicken and place in a baking dish. Roast for 1 hour or until the skin is golden and the chicken is cooked through.
To make the herb sauce, heat the oil in a frying pan over high heat. Add the garlic, onion, bread and pine nuts and cook for 5 minutes or until golden. Place in the bowl of a food processor with the sage, parsley, chicken stock and pepper and pulse until roughly chopped. Return to the pan and heat over medium heat for 2–3 minutes or until warm.
To make the sage salt, place the sage and salt in the bowl of a small food processor and pulse until just combined. Serve chicken with the herb sauce and sprinkle with sage salt. Serves 4.