Score 3 diagonal slits along each side of the fish with a sharp knife, then cut in the opposite direction to make a diamond pattern.
Cut 2 large pieces of foil about 1½ times the length of the fish. Place the fish in the centre of the double layer of foil and lift it up around the fish slightly. Pour the stock and rice wine over the fish, then scatter with the orange rind and half the ginger.
Place a circular rack inside a wok and pour in enough water to come just below the top of the rack. Place the lid on the wok and bring the water to a rolling boil. Carefully sit the open fish parcel on the rack, cover with the lid and steam for 15–18 minutes until the flesh inside the slits is opaque. Carefully remove the fish from the wok and place on a serving dish.
Stir the sugar into a bowl with the soy sauce and sesame oil, then pour the liquid over the fish with the garlic, spring onions and remaining ginger.
Heat the groundnut oil in a small frying pan over a high heat until smoking hot, then pour it over the fish. This will crisp up the spring onions and ginger and release their aroma. Serve immediately.