Meanwhile, heat some oil in a pan, fry the mixture very gently in the oil until the onions are translucent
Add the turmeric, ginger and cardamom and let it fry for a while
Add the can of tomatoes and simmer gently for 15 minutes
Add the coconut milk, stir well and simmer again. The curry can get quite thick, the water from the mussels will dilute it later
While the curry is simmering, rinse the mussels and check them according to package instructions
Add the mussels to the curry, stir well until all mussels are coated in curry. Put a lid on the pan and heat for another 4 minutes or until all the shells are open. Toss again halfway through so that the mussels cook evenly.
Serve with the fresh coriander and season with salt and pepper