For the Marinade: Make the marinade by combining all the ingredients for the marinade together in a bowl. Bring to a boil and reduce to a gentle simmer. Cook until the sauce reduces and becomes glossy. This will take about 10-15 minutes. Allow to cool completely, then mix half the marinade with the chicken and set aside for at least 20 minutes. Reserve the remaining marinade to baste the chicken and serve alongside the finished dish.
For the Rice: Rinse the rice under cold water until the water runs clear. Combine rice and 450ml of water in a saucepan, then bring to a boil. Reduce to a low simmer, cover, and cook 12–15 minutes until tender. Rest covered 5–10 minutes, then fluff with a fork.
For the Chicken: Heat an overhead grill to high. Once hot, place the chicken on a foil-lined grill tray and grill for 10-12 minutes on each side, until no red remains, or it reaches 75 °C on a meat thermometer. Baste the chicken with the pan juices and brush with fresh teriyaki sauce every 5 minutes.
For the Bak Choi: Bring a pan of salted water to the boil. Cook the Bak choi quarters for 1 minute until the stalks are tender.
To serve: Serve the chicken on top of the rice with two quarters of Bak choi per person. Garnish with spring onion and sesame seeds.