Special equipment: kitchen string
1) Preheat to 200°C/gas mark 6.
2) In a bowl, combine the sausage, prosciutto, chestnuts, olives and sage. Season with salt and pepper. Heat a small skillet and add one teaspoon of the stuffing. Saute until cooked through, about two minutes. Taste for seasoning and adjust seasoning in the stuffing mix, if necessary.
2) Place the turkey breast on the cutting board with skin side down. Flatten with your hands, season with salt and pepper and drizzle with olive oil to moisten. Spread stuffing on top and roll the turkey around the stuffing. Wrap kitchen string around breast and tie tightly.
3) Place turkey in a roasting tin, drizzle with olive oil and season with salt and pepper. Roast until internal temperature of the turkey breast is 74°C, about one hour or 25 to 30 minutes per 500g.
4) Let rest 10 mins, then snip off kitchen string. Slice the turkey and arrange decoratively on serving platter. Pour pan juices over the slices and serve.