In mortar and pestle bash together lemon grass, ginger and lime leaves.
Place in a pot with the stock, bring to the boil and simmer for 10 minutes.
Place in a pot with the stock, bring to the boil and simmer for 10 minutes.
Add xylitol and lime juice to taste.
Add prawns and cook for 1 minute.
Remove prawns, add to the bowl, pour over broth and garnish.