Heat the oil in a large, flat bottomed pan.
Add in the lemongrass, garlic and ginger and fry for 1 minute to release the flavours. Do not let them burn.
Quickly place the clams in the hot pan and cover with a lid or a plate. The clams are still alive at this point so it is essential that you do this quickly to minimise their suffering.
After 1-2 minutes, shake the pan around and remove the lid.
The clams should all have opened and released a lot of juice into the pan. Spoon the juice over the top of the clams to get the flavour into the shells.
Sprinkle with the lime juice, chilli, spring onion and coriander and serve.