Add 100 mls of the coconut milk and curry paste and fry until the coconut milks spits and smells fragrant. Add sugar and fish sauce then cook for 5 minutes. Add lime leaves and remaining coconut milk and bring to the boil.
Add the mussels, reduce the heat to medium then cover saucepan with a lid. Cook for about 4 minutes or until the mussels open, add the lime juice and coriander and give the pot a shake. Divide between plates and pour sauce over the top.