Heat the oil in a large saucepan or frying pan add the spring onions for a minute then the curry paste.
Whisk in the coconut milk, chicken stock and fish sauce. Bring to the boil.
Tip in the squash and sweet potato cubes and simmer, partially covered for about 15 mins.
Drain the prawns under water to remove excess ice add them to the pan letting the sauce come back to the boil and then add the lime juice and mango, cook for another minute or so. I like my sauce quite runny like authentic thai but if you like a thicker sauce you could at this point add some cornflour.
Sprinkle with the chopped coriander and serve with basmati rice. Yum!