Put in the turmeric, cook for 20 seconds more before tossing in the squash and whole green chillies. Stir fry for a couple of minutes, add the water, bring to the boil, lower the heat, cover and cook till the squash is tender but not squishy.
Now season with salt and chilli powder keeping the heat low. Finally pour in the coconut milk and simmer for a further 2 minutes. Serve with hot rice or rotis.