Heat the chicken stock in a non stick wok. Chop lemon grass root, lightly crush them and add to the wok.
Add celery and roughly chopped ginger. Add onion, shelled prawns and 2 unshelled prawns. Halve fresh red chillies and add along with tomato paste.
Break the coriander stems and add along with coriander leaves and mix well. Add salt and mix.
Remove the unshelled prawns and set aside. Strain the mixture and put the strained stock back into the wok and simmer.
Cool the solids slightly and put into a mixer jar. Add white wine and grind till smooth. Add this to the simmering stock in the wok and mix well. Add coconut milk and mix well.
Place the unshelled prawns on the rim of a soup bowl. Pour the bisque into the bowl. Garnish with a sprig of fresh coriander and serve piping hot.