2.5kg (5.5 lb) lamb leg
3 red onions, halved
6 rosemary sprigs, plus extra rosemary leaves to serve
2 cups Chinese Shaoxing wine
3 tbsp soy sauce
1/3 cup miso paste
1 tbsp honey
Tomato miso sauce:
1 x 400g (14 oz) tin whole peeled tomatoes
1 tbsp miso paste
2 tbsp oyster sauce
1 tbsp white vinegar
2 star anise
Use a sharp knife to score the lamb fat. Place the onions in a roasting tray and top with the rosemary sprigs. Place the lamb on top.
Combine the marinade ingredients. Pour the marinade over the lamb and rub all over. Cover and allow to marinate in the fridge overnight or at least 6 hours. Remove the lamb from the fridge at least 2 hours before cooking so that it loses some of the chill.
Preheat the oven to 150°C/300°F.
Pour the Chinese Shaoxing wine into the roasting tray. Cover the lamb with baking (parchment) paper, then cover and tightly seal with foil. Roast for 3½ hours.
In the meantime, combine the ingredients for the tomato miso sauce in a saucepan over medium-high heat. Bring to a simmer and use a wooden spoon to break up the tomatoes. Turn the heat to low and simmer for 10 minutes. Remove from heat and set aside until the lamb is ready.
Remove the lamb from the oven and uncover. Turn the oven heat up to 200°C/390°F.
Ladle most of the cooking juices into the tomato miso sauce, saving a couple of spoonfuls of cooking juices to baste the lamb. Place the lamb back into the oven uncovered and roast for 30 minutes or until deeply browned.
In the meantime, place the tomato and miso sauce back on a high heat and simmer for 5 minutes to thicken slightly. If the sauce contains a lot of lamb fat, use a paper towel to soak it up or spoon it off with a ladle. Allow the lamb to rest for 20 minutes. Then carve and serve with the tomato miso sauce and a sprinkling of rosemary leaves.