In a small bowl, mix all of the ingredients, except the fish and the pak
choi, together to make a soy mix. Line one tier of a two-tiered bamboo
steamer loosely with foil. Lay the fish, skin side up, on the foil and spoon
over the soy mix. Place the fish over simmering water and throw the pak
choi into the second tier and cover it with a lid. Alternatively, add the
pak choi to the fish layer after 2 mins of cooking – the closer the tier
is to the steam, the hotter it is.