- In a sauce pan, bring water to the boil over medium heat.
- Boil the prawns’ heads and peels for 2 mins and remove. Use only the stock.
- Bring the stock to the boil, adding lemongrass for half a minute, then add mushroom, prawns, kaffir lime, fish sauce, lime juice and chilli.
- Remove from heat and serve in soup bowls. Garnish with fresh coriander.