Clean mussels discarding any with cracked or broken shells and set aside. Finely slice the onion, garlic, ginger and chilli and mix together. Place a large flat base saucepan over a low heat and add the olive oil. Gently cook the onion, garlic, chilli and ginger for 3 minutes. Turn the saucepan up to a medium to high heat and add in the mussels and Simon Gault Home Cuisine fish stock. Cover the saucepan with a lid and cook for 6 minutes or until the mussel shells have opened. Remove mussels from the heat, discard any mussels that do not open during cooking and remove the tongues and beards. To debeard your mussels, pull the threads down towards the pointy end of the shell, discarding the brown foot and any muscle attached to the shell. Place in large serving bowl to keep warm. Add coconut milk to pan and cook until the coconut milk has reduced by half. This should take approximately 10 minutes over a medium heat. Squeeze in one of the limes. Place the debearded mussel meat back into their shells and pour the sauce over the cooked mussels. Sprinkle mussels with chopped coriander and serve with a green salad, a wedge of lime and plenty of crusty bread to mop up the juices.