Step 1 Place bok choy leaves in a colander and pour over boiling water until they are just beginning to soften. Place ginger slices and spring onions on top of each salmon fillet. Wrap bok choy leaves around them, folding under the bottom of each piece of salmon.
Step 2 Place salmon in the steamer of your choice. (Bamboo steamers are traditionally used for this type of dish but any will work.)
Step 3 Fill a saucepan with boiling water, then bring the water to a rolling boil.
Step 4 Place the steamer on top of the pan, ensuring that it is a snug fit. Cover the top of the steamer with a lid. Take care when placing the steamer on top of the pan and use a cloth or oven mitts to prevent scalding from the steam. Steam for 10–15 minutes.
Step 5 Meanwhile, combine sesame oil, soy sauce, rice wine vinegar and sugar in a saucepan with 1 tablespoon water and bring to the boil.
Step 6 The fish is done when it is a pale pink colour and flakes easily when broken with a fork. Serve salmon with sauce and steamed rice or noodles.