1. Remove heads and shells from prawns and run a sharp knife along the back of each to remove the black vein. Toss the shells and heads into a pan, cover with 750 millilitres of water and simmer for 15 minutes. Sieve out the prawny bits and set aside. Return the pan to the heat and fill it up with boiling water. Plunge in the beans and the noodles for 30 seconds, then strain and set aside in one of the bowls.

2. Over a medium heat, fry the laksa paste in the vegetable oil for five minutes. Add the juice of one lime, sugar and fish sauce. Then gradually pour in the prawn stock and coconut milk. Simmer for another five minutes, then add the bean sprouts and prawns. Cook until the prawns are piping hot and pink (about eight minutes).

3. Finally, stir in the beans, spring onions and coriander and serve over the noodles.