Wash & dry the fish chunks then rub them with salt.
Place them on a heat-resistant plate, sprinkle the ginger, orange and lemon zest over them. Put the plate into a bamboo steamer.
Add water to a wok up to a depth of 5 cm, then heat it. When boiling, put the bamboo basket in the wok, making sure the bottom of the steamer doesn't touch the water. Cover the steamer and cook for 5 minutes. Don't overcook - the fish should be fluffy but not transparent.
Transfer the bamboo steamer to a plate. Carefully remove the fish and put it in a serving dish. Sprinkle the spring onion and basil leaves over then drizzle with soy sauce.
Wipe the wok clean and heat the two oils in it until piping hot (i.e smoky). Pour this over the fish and serve while sizzling.