Scrub the mussels clean. Discard any mussels that don't close when tapped gently.
Set up a steamer or put a rack into a wok or deep pan and fill it with 5cm/2in of water. Bring the water to the boil over a high heat.
Place the mussels on a plate, then place the plate into the steamer or onto the rack.
Turn the heat to low so the water is barely simmering and cover the wok or pan tightly.
Steam gently for five minutes or until the mussels begin to open.
Meanwhile, combine all the sauce ingredients, except the oil, in a heatproof bowl.
Heat a wok or large frying-pan over high heat. When hot, add the oil. Heat the oil until it's very hot and slightly smoking, then pour the hot oil over the sauce ingredients.
Remove the mussels from the steamer. Discard any mussels that haven't opened.
Stir the sauce then pour over the mussels.
Garnish with fresh coriander sprigs and serve at once.
