Heat the oil in a saucepan. Gently fry the cumin, turmeric, chilli powder, ground coriander and curry powder for 1 minute.
Add the onion, ginger and garlic and fry, stirring, for 5 mins. Add the squash and cream, bring to the boil and then immediately reduce the heat to a gentle simmer. Cook for 10 mins, uncovered, then add the green beans and simmer for a further 5 minutes uncovered.
Add the prawns; simmer for 5 mins. Season to taste, add the lime juice and chopped coriander to taste. Serve with boiled rice on the side.