Scrub and debeard the mussels and clams if needed. Rinse well in cold water. Discard any that don’t close when tapped shut.
Heat the oil in a large pan. Fry the onion until it turns a light brown, adding in the ginger, garlic, chillies, spices and a pinch of salt and pepper. Cook the spices for 2-3 minutes until toasted. Then pour in the coconut milk and bring to the boil, then to simmer for 10 minutes to get everything mixed together well.
Tip in the mussels and clams into the pan, covering with a lid and turining up the heat and boiling for 3-4 minutes until the shells have opened. Discard any with closed chells. Scatter over the fresh coriander and servees with the lime wedges.