Clean the fish well. Score the fish lightly with a sharp knife, no more than halfway to the bone, making 3 diagonal slashes on each side. Rub the combined seasoning mixture over the fish to coat it lightly; dust off excess.
Deep-fry the fish until golden and cooked through.
Discard the oil and place the fish in the wok. Pour the sauce ingredients over the fish. Put in garlic, ginger and spring onion. Reduce the heat and allow the mixture to simmer gently. Cover the wok for 56 minutes. Open the wok cover and turn the fish around, coating it with the sauce. Dish out and serve.