Cut the pak choi in half, or into thick slices if large, and put in a steamer basket. Lower into a shallow saucepan of boiling water so that the pak choi is not quite touching the water. Cover and steam for 2–3 minutes or until tender. Alternatively, use a bamboo or electric steamer.
Heat a large wok or frying pan over a high heat until smoking hot, add the oil, garlic and ginger and stir-fry for 30 seconds. Add the vegetables and stir continuously for 2–3 minutes or until beginning to wilt.
Pour over the sweet teriyaki sauce, toss to combine and serve immediately with the steamed pak choi and steamed rice, if liked.