Soak the sliced mango in water. Keep aside.
Grind the coconut with turmeric powder, coriander powder, chilli powder, ginger paste, clove and enough water, to a smooth, fine paste. Keep aside.
Remove the mango slices from the water. Keep the water for later use.
Take an earthen pot.
Put the cleaned fish with curry leaves, mango slices, salt and green chillies and mix well.
Add the ground paste to the fish. Add enough water.
Cook on medium heat till the fish is cooked through.
Check and adjust the seasoning.
If you want more sourness, you may add the water in which mango was soaked.
Switch off heat. For Tempering
Heat oil in a pan.
Add mustard seeds.
When they start to splutter, add the shallots and curry leaves.
Saute till the shallots turn brown in colour.
Add the fenugreek powder and mix well.
Pour the mixture over the fish curry.
Serve the curry with Rice or any Indian bread of your choice.