Divide the oysters between 2 heatproof plates that will fit inside 2 large stacking bamboo steamer baskets. Cover and steam over a wok or large saucepan of boiling water (see
Meanwhile, for the sauce, combine all the remaining ingredients in a small bowl.
Lift the oysters from the steamer baskets and carefully remove the top shell of each oyster. Spoon a little of the sauce over each steamed oyster and serve immediately with shredded spring onion and steamed rice, if liked.