Combine the sherry, sugar, oil and half the soy sauce in a small jug.
Place the fish in a shallow heatproof bowl (make sure the bowl fits inside your steamer). Top with the ginger and pour over the sherry mixture.
Place the bowl in the steamer over a wok one-third filled with simmering water (make sure the steamer doesn’t touch the water). Cook for 5 minutes or until the fish flakes easily when tested with a fork.
Divide the Asian greens and fish among serving plates. Drizzle over the remaining soy sauce and any juices from the bowl. Top with the shallot and chilli, if desired.