Peel the mangoes and cook the peeled mangoes with salt and 1-1/2 cups of water for 10 minutes.

Grind together coconut, jeera, garlic, small onion, green chili and turmeric powder with 1/2 cup of water to a fine paste. Add this and 1 cup of water to the mangoes. Check salt and add more if required.

Cook for 5-7 minutes on low flame. Make sure that it doesn't boil. Remove from fire.

Heat oil in a pan and splutter mustard seeds. Add sliced small onions, red chili and curry leaves. Fry till the onion becomes golden brown. Pour this over the curry. Let it rest for a while for the flavors to settle in. 

Serve with rice.