Using a mortar and pestle (or a food processor), blend the onion, ginger, garlic, lemongrass, chillies, macadamia nuts and shrimp paste into a paste. Meanwhile, soak the rice vermicelli in cold water for about 20 minutes.
Heat a wok, add 3 tablespoons oil and bring to high heat. Fry the paste for five minutes but do not allow to brown. Reduce heat to low and add coriander, paprika, turmeric and cumin and simmer, stirring often, for two minutes.
Add coconut milk, stock, sugar and salt to the paste and bring to the boil. Meanwhile, pour boiling water over the vermicelli and the hokkien noodles, leave for two minutes and rinse.
Distribute the noodles, the vermicelli, beans, beansprouts, chicken and prawns in four deep bowls. Add hot stock to each bowl and scatter mint leaves on top.