Soak all the ingredients mentioned under for soaking and grinding for 2 hours.
Grind them in a wet grinder or a blender to a smooth thick batter. Add salt as needed. Wash the grinder/mixer with a cup of water and reserve the water.
Make the porridge or kurukku by mixing up the ingredients mentioned under 'for kurukku' and heating up on stovetop with constant stirring till it cooks and reaches a porridge consistency.
Let it cool down a bit and add it to the ground batter. Let it ferment for at least 6 hours or overnight.
Next morning, extract 1 cup of coconut milk by grinding the coconut with warm water and straining it.
Mix this with the fermented batter and also add the residual rice paste from the grinder-washed water. Add the water too as needed to bring it to a dosa batter consistency.
Taste test the batter and add salt and sugar as needed. Mix well and let sit for 15 minutes.
Heat up the aapam pan or aapachatti on medium heat. Wipe the pan with oil. Pour a ladle in the center of the pan. Lift the pan using the handles at the side and gently swirl the pan so that the batter coats the entire pan. Smear oil, cover, and cook for a minute or two.
Remove from the pan once the centre gets cooked and the edges brown up. Serve with coconut chutney, ishtu, vegetable ishtu, sweetened coconut milk, kadala curry, chicken or mutton curries.