Put about half an inch of water in the bottom of a pan, into which your steamer will fit
Put the steamer in the pan and line it with cabbage leaves. Although you will serve the fish in the leaves, they are not particularly pleasant to eat because they will be very overcooked - so you may wish to discard them!
Blitz all the marinade ingredients together, then pour over the fish and leave for at least 15 minutes and up to 2 hours
Once the fish is marinaded,lift it carefully out of the marinade and place on the cabbage leaves with the spring onion scattered on top. Put the lid on the pan.
Steam the fish at a gentle simmer for about 15 minutes (this will depend on the thickness of your fish)
Serve with plain or jasmine rice and with any remaining marinade poured over