1. How to make the marinade: Use a fork to poke some holes on each side of the meat, and then put the barbecue into a large plastic food bag. Mix the soy sauce, sherry, honey, garlic and ginger in a medium bowl, pour it into the food bag, remove excess air and tie the bag tightly. Refrigerate for more than 8 hours or overnight, turning the food bag several times in between.

2. Preheat the oven to 165 degrees Celsius.

3. Take the barbecue out of the refrigerator and keep the marinade. Place the roast on a 22?x32cm baking tray and bake in the preheated oven for 1 hour. Then brush with the reserved marinade, wrap loosely with foil and bake for another 1.5 hours (or until the internal temperature of the meat reaches 70 degrees Celsius), brushing with the reserved marinade several times during this time.

4. Take the roast out of the oven and leave it for 15 minutes. Mix any drippings from the pan with the marinade. Mix cornstarch and cold water in a small bowl, then pour in the mixed oil and marinade. Cook it for 4-5 minutes or until the juice is thick and serve with grilled meat.