Sprinkle 1/2 teaspoon yeast with warm (approximately 105 degrees F) coconut milk. Add 1/2 tablespoon sugar and mix well. The yeast should begin to form a creamy shape on the surface of the water and let it sit aside for 10-20 minutes until frothy. That implies that yeast is active. As suggested in the recipe, you can now continue to use the yeast.
Add 2 tablespoon of rice flour and 1 cup of water into the pan. Let it boil slowly by constantly stirring. When it is thickened switch off the heat and add 1/2 cup sugar. keep it aside to cool.
Mix remaining rice flour and frothy yeast. Add enough coconut milk to mix it to a soft dough. Cover and keep it for an hour.
Add grated coconut to the blender and add enough coconut milk to grind it to paste. Then add cooked rice flour and sugar into the blender and blend again until well combined. Add cardamom, salt, rice flour soaked earlier little at a time to the blender and mix all together to a consistency like idly batter. Use coconut milk to blend it. Adjust sugar to your taste.
Keep it in warm place for fermentation for about 6-8 hours or overnight
Grease a pan or idli pan with ghee or coconut oil, then pour the batter to fill half of the pan
Garnish with raisins, cashews
Steam it for 30 minutes or until it is cooked, over medium heat
When it is cooked, remove it from the steamer and let it cool before you cut the vattayappam. Serve it with hot tea or coffee