Season the barramundi with salt. Place 1/3 ginger and spring onions on to a plate, place barramundi on top. Scatter the remaining ginger and spring onions over the barramundi.
Heat a pan with water, until boiling. Put the dish on a rack over the boiling water, cover and steam for 8-10 minutes. Pour out any water that may have collected in the dish.
Mix together the soy sauce, sugar and hot oil; pour over the barramundi and serve.