In a large non-stick frying pan, heat the half of the peanut oil over medium-high heat. Cook the lamb for 8 to 10 minutes, or until browned on all sides.
Meanwhile, in a large bowl combine the soy sauces, vinegar, half the ginger, 2 cloves garlic, lemongrass, chilli, star anise and half the sesame oil. Place lamb in a roasting pan and pour sauce over lamb, brushing to coat. Roast lamb for 60 minutes for rare, 75 minutes for medium or 90 minutes for well done, covering with foil if overbrowning.
Once lamb is cooked to your liking, remove meat from pan and set aside covered in foil for 15 minutes. Skim any fat from the sauce, and strain into a bowl.
For the sesame rice heat the remaining peanut oil in a large non-stick frying pan over medium-high heat. Cook the onion with the remaining ginger and garlic for 1 to 2 minutes or until slightly golden. Add ¼ cup of reserved sauce and simmer for 1 to 2 minutes. Add the Chinese broccoli, capsicum and sugar snaps and cook for 1 to 2 minutes. Add rice and heat through for 1 to 2 minutes. Remove from heat and toss through sesame seeds.
Serve lamb with reserved sauce and sesame rice topped with green onions and coriander.
Any leftover lamb is delicious in Chinese pancakes with cucumber and shallots.
The marinade would also be great for lamb shoulder, or lamb chops.
You can use any type of rice (jasmine, basmati, long grain) for the sesame rice.