Grind the coconut along with turmeric powder, coriander powder, chilli powder and 1 tablespoon water to a coarse mixture.
Take a bowl and put the sardine pieces, shallots, garlic, ginger, green chillies, curry leaves, a bit of salt and the ground coconut mixture.
Mix well. Cover and keep aside for at least 10 minutes.
Wash the gambooge very well. You may tear each of them to 2-3 pieces.
Take an earthen pot with 1/2 cup water.
Add salt, 1/2 teaspoon turmeric powder and few curry leaves and bring to a rolling boil.
Add the fish mixture and mix well.
Cover and cook on low flame.
Occasionally lift the earthen pot and toss so that the mixture in the bottom come to the top.
You can use a spoon to stir but there are chances of crumbling the fish pieces. Hence tossing would be better.
Once the fish pieces are cooked, remove the lid and cook till the liquid, if any, has evaporated.
Switch off heat
Serve with rice.
The dish gets tastier after a couple of hours. So it is recommended to prepare the dish well in advance.