Blanch the ashgourd in water (with just a pinch of salt added to it) till just tender. Drain from water, keep aside.
Marinate the prawns with a little salt and a pinch of turmeric powder.
Heat oil in a pan, shallow fry the prawns till light pink. Keep aside.
To the same oil, add the curry leaves, let them splutter. Now add the chopped onions. Fry till soft and translucent.
Add the above temperado masala paste, sprinkle in the remaining turmeric powder, cook over a medium-low flame till oil starts to get released from the masala.
Carefully pour in ¼ cup of warm water, add the coconut milk, throw in the fried prawns, ashgourd and green chilies, bring to a gentle simmer.
Cook over a low flame for 10 odd minutes, till the curry has a medium thick consistency. Allow to rest for 10minutes.
Serve hot with steamed rice or appams or neer dosa.