Cook the noodles in a large shallow casserole pan according to the packet instructions. Meanwhile, tap any open mussels and if they don’t close, discard them. Prick the aubergine, then carefully blacken over a direct flame on the hob (or under the grill), turning with tongs until charred all over. Drain the noodles, leaving them in the colander, and return the pan to a high heat. Trim the spring onions, chop the whites into 1cm lengths and place in the pan, putting the green tops aside. Finely chop and add the coriander stalks, reserving the leaves. Finely grate in the lime zest, stir in the laksa paste for 1 minute, then pour in the coconut milk. Add the mussels, cover the pan and leave for around 4 minutes, or until the mussels have just opened. If any mussels remain closed, discard them.
Finely slice the green spring onion tops. Tear up the coriander leaves. Use a spoon to scrape off most of the blackened aubergine skin (it will have imparted a lovely smoky flavour), then roughly chop the flesh and stir into the pan with the noodles. Season the broth to perfection with lime juice, sea salt and black pepper, and serve sprinkled with the green spring onions and coriander leaves.