Combine shoyu, oyster sauce and honey in a medium bowl. Add lamb and toss well to coat. Put in the fridge to marinate for 10 minutes. Drain, reserving the marinade.
Heat a wok over high heat. Add 3 tsp oil and heat until hot. Add half the lamb and stir-fry for 1 minute or until brown. Remove to a plate, cover and keep warm. Repeat using 3 tsp oil and remaining lamb.
Add remaining oil to wok and heat over high heat until hot. Add onion and stir-fry for 1- 2 minutes. Add mushrooms and broccolini and stir-fry for 1-2 minutes.
Add capsicum, reserved marinade and lamb and stir-fry for 2 minutes or until capsicum is tender. Serve with steamed basmati rice or freekeh.