Bring the stock to a simmer in a large
pan. Add the lemongrass, lime leaf or
zest, ginger, fish sauce and as much chilli
as you like. Simmer for 20 mins. Add the
cabbage and simmer for another 30 mins
until it is very soft. Add the carrots and
beans, and simmer for 3 mins. Top up
with more boiling water if necessary.
Put the rice noodles in a bowl and
pour over the boiling broth. Serve with
a wedge of lime to squeeze over.