- Preheat oven to 350°F (160°C). Soak panko in milk for 2 minutes. Stir in mozzarella, sun-dried tomatoes and parsley to combine.
- Lay meat, fat-side-down, and season all over with salt and pepper. Spread evenly with stuffing mixture leaving a 2-inch (5 cm) border at each end. Starting at a narrow end, roll meat up, jellyroll-style and tie with kitchen twine.
- Transfer roast to a rack set in a roasting pan. Roast for 1 hour. Blend butter with vinegar and honey. Brush over lamb, continue to roast, basting occasionally with pan juices for 30 minutes or until a meat thermometer inserted into the center registers 160°F (71°C) for medium (or to preferred doneness). Tent with foil and rest for 20 minutes. Slice thickly to serve.
- Ask the butcher at the meat counter to butterfly the roast for you, making the preparation even easier.