Make the laksa paste: put all the ingredients together in a food processor. Add 5 tbsp of the coconut milk and whizz together to form a green paste.
Heat a large sauté pan or casserole for 1 minute. Add the paste and stir over a low heat to fry the paste and soften the ingredients. Add the butternut squash, remaining coconut milk, ginger or galangal, kaffir lime leaves, and season with salt and pepper. Bring to the boil and simmer for 12-15 minutes until slightly reduced and the coconut is showing signs of separating.
Meanwhile, cook the rice vermicelli according to the packet instructions, drain and set aside.
Add the green beans to the laksa and cook for another 2-3 minutes or until they are cooked. Adjust the seasoning and add the lime juice.
Discard any mussels that are open, cracked or damaged. Add all the seafood at the same time as the green beans and cook over a low heat, for 2–3 minutes or until the plaice flakes, all the mussels are open (discard any that don’t open) and the prawns are cooked through.
Divide the noodles between 6 soup bowls and ladle the laksa on top. Garnish with sprigs of coriander and serve immediately.