Rinse and drain fish.
On both sides of fish, cut deep incisions across width at 3 cm (1") intervals.
Sprinkle with salt inside and out.
Cut spring onions into 2 or 3 sections, then slice lengthways into thin strips. Julienne ginger slices. Insert spring onions and ginger into incisions – any excess can be placed inside fish.
Place fish in a steamer. Steam on a medium heat for about 10 minutes.
Place fish on a serving dish.
Mix soy sauce and vinegar and pour over fish.
Remove water from wok. Add oil to wok, heat till sizzling and pour over fish.
Garnish with chopped coriander and serve.