In a Mannchatti/ earthern vessel ( mostly preffered) add together onions,ginger, green chillies,curry leaves,dry spice powders,salt,thin coconut milk,2 tbsp coconut oil,5 shallots and mix with hands.
Switch on the flame and let it boil.
Add mango pieces when it starts to boil.
Add vinegar and cover and cook for 10 mins.
Switch off the flame and add thick coconut milk.
For tempering,heat 2 tbsp oil,add mustard seeds,let it splutter.
Add dry red chillies,curry leaves and chopped shallots and toss for few seconds.
Add this to the gravy and keep it covered for sometime before serving.