Preheat the oven to 200°C conventional oven/ 180°C fan-forced (400° Fahrenheit/Gas 6). Line a large baking tray with baking paper.
Season the chicken with salt and freshly ground black pepper inside the chicken’s cavity. Place 1/2 of the onion, 1 sprig rosemary, 1 sprig thyme and the 1/2 lemon inside the chicken’s cavity.
Roughly chop the remaining onion, rosemary and thyme and arrange in the baking paper lined baking tray. Add the garlic, carrots and celery in a single layer to the baking tray with onion and herbs.
Place the chicken in the baking tray on top of the vegetables, breast side up and drizzle with the olive oil. Season the outside of the chicken with salt and pepper. Then sprinkle with ariosto and pour over the chicken stock mixture. Roast for 20 minutes then remove from the oven.
Pour the white wine over the chicken and baste with pan juices. Then arrange the prosciutto and sage leaves, overlapping slightly, over the chicken breast.
Optional – you may choose to use kitchen twine to tie the chicken to secure the prosciutto and sage leaves. This will reduce the rippling of the prosciutto and sage.
Reduce the heat to 180°C conventional oven/ 160°C fan-forced (350° Fahrenheit/Gas 4) and continue to cook, basting occasionally in pan juices, for a further 1 hour or until golden all over and cooked through (the juices should run clear when a skewer is inserted into the thigh).
Remove the onion, lemon and herbs from the chicken’s cavity. Transfer the chicken to a serving dish, cover loosely with aluminium foil and set aside to rest for 10-15 minutes before serving – buon appetito.