Heat half the oil in a large heavy-based saucepan. Cook the turkey over a medium heat for five minutes, until golden brown. Set aside on a plate. Add the remaining oil and squash and fry for 3-4 minutes, before adding the coriander and basil stalks, turmeric and laksa paste. Cook for one minute and then pour in the coconut milk, along with a can full of cold water and the fish sauce.
Simmer gently for 8-10 minutes, or until the squash is just tender. Blend about half the soup in a food processor until smooth. Return this to the pan. Meanwhile, cook the noodles according to pack instructions.
Add the turkey and the beansprouts to the soup. Bring to a simmer and cook for a further five minutes until everything is piping hot. Add the noodles, lime zest and juice, season with fish sauce and divide between bowls. Scatter over the reserved herb leaves and serve with extra lime wedges and sriracha chilli sauce, if you like.