In a large resealable plastic bag, mix hoisin sauce, rice vinegar, spring onions, soy sauce, garlic, honey, sesame oil, sesame seeds, white pepper and black pepper. Place lamb in bag, seal, and turn to coat. Refrigerate for 8 hours, or overnight.
Preheat your barbecue for high heat.
Oil the cooking grate. Place lamb on the grate and discard marinade. Cook 15 minutes on each side, to a minimum internal temperature of 63 degrees C, or to desired doneness.
Transfer meat to a serving platter, and allow it to rest for 15 minutes before slicing and serving.