First wash your clams well under cold running water, throwing away any that are not tightly closed. Drain in a colander and put to one side.
Prepare the noodles according to the packet instructions, but cook for only half the listed cooking time. Set aside.
Peel and finely slice the galangal or ginger and the shallot, then deseed and finely slice the chillies. Pick the coriander leaves and finely chop the stalks.
Find a wide saucepan – big enough to hold all the clams and noodles together comfortably – and place it over a medium heat.
Add a splash of oil and fry the chilli paste for a few seconds, until the oil turns red, then add the galangal, chillies, shallots and coriander stalks and cook for 2 to 3 minutes, or until the shallots soften.
Add the clams and lime leaves, fry for a few seconds, then add the vinegar and 2 tablespoons of water.
Pop the lid on and cook over a high heat for 2 to 3 minutes, shaking the pan every now and then, until all the clams have opened.
Take the pan off the heat and stir in the noodles. Stir in the clams, add a splash of fish sauce and the juice from 1 lime, then cover with a lid and leave for a couple of minutes.
Divide among bowls and serve with coriander leaves and lime wedges.