Wash and peel the ginger by using a peeler or a knife; just as you would with a carrot. Slice it diagonally or transversally. Leave aside.
Wash the spring onions and shake off the excess water. Then cut them julliene style. It they are too thin and difficult to julienne, then finely slice them in a diagonal direction. Leave aside.
Wash the coriander and shake off the excess. Roughly chop them and leave aside.
The fish should be as fresh as possible and thoroughly scaled. Even though they would do this at the fish shop, you should make sure by yourself.
Use a knife to remove any scales that might be left (always from tail to head – opposite to the scales direction), paying special attention to the head and the areas near the fins.
Use kitchen shears to trim the fins. Leave the tail whole for presentation purposes. Check the cavity and the gills and remove any leftovers.
Wash and shake off the excess water.
Make a diagonal cut on each side of the fish. This will help to cook the fish evenly and it will be easier to check if it is done.
Rub the salt on the fish.
Place half of the ginger in a heat-proof dish, put the fish on top and then cover with the remaining ginger.
Use a wok or a saucepan big enough to hold your heat-proof dish. Place a metal steam rack and add water. Bring to a boil, then place your heat-proof dish with the fish and put the lid on.
Steam for about 15-20 minutes, until the fish is done. You can look into the diagonal cut and the flesh should be opaque all the way to the bone.
Meanwhile, when the fish is nearly done, put the oil in a frying pan over high heat.
Carefully remove the heat-proof dish (remember that it will be very hot). Drain the liquid, lift your fish with care and place in an elongated presentation plate, which should be heat-proof too. Remove the ginger.
Sprinkle the spring onions and coriander on top and pour the soy sauce all over.
When the oil is smoking hot, carefully pour it over the fish. Be very careful, while handling the hot oil.