First of all, you need to prepare the seafood.So, peel the prawns, then run the point of a small, sharp knife along the back of each one and remove any black threads that may be present. Now scrub the mussels under cold running water and remove any barnacles and pull off the little hairy 'beards'. Discard any mussels that are broken or don't close when given a sharp tap with a knife.Now place the rice noodles in a bowl and cover with boiling water, then leave to soak for 10 minutes – they won't need any further cooking, just re-heating. Then drain the noodles in a colander when they are ready, rinse them in cold water and set aside.Next, to make the paste, place all the paste ingredients, plus a tablespoon of water, into a blender or the bowl of a food processor and blend until smooth. Now place the macadamias or peanuts in a medium saucepan and dry-roast over a medium heat until golden brown, then remove to a plate. Add the oil to the same pan and, when warm, add the prepared paste and cook over a medium heat for 2 minutes. Add the coconut milk and stir, then leave to simmer gently for 10 minutes.Meanwhile, cut the cucumber into four slices lengthways, then cut each into four long strips. Next, roughly chop the toasted nuts.When the coconut-milk mixture is ready, add the noodles, cucumber, three-quarters of the beansprouts and the lime juice. Now season to salt, with taste, then bring back to a simmer, add the prawns and mussels and cook for 3-5 minutes – the prawns should turn a pretty pink colour and all the mussels should open. Discard any mussels that don't open during cooking. Now add half the shredded herbs, then mix the remaining herbs with the chopped nuts. Finally, ladle the laksa into four deep bowls, then sprinkle over the remaining beansprouts and the herb mixture.