Wash and then soak the raw Basmati rice in a large bowl for 4-5 hours or over night.
Once soaked, mix the raw and cooked rice together in a food processor. Add the coconut milk to the mix and blend till a smooth paste is formed.
Pour the batter into a bowl.
Add a little water at a time if needed to get a batter with pouring consistency - like thin pancake batter.
Warm a cup of water till tepid. Add the sugar, salt and yeast to this water and stir. Add this to the above batter and mix well. Leave the batter overnight at room temperature to ferment.
When you are ready to make the Appams, heat a small non-stick kadhai (wok) on medium flame and pour a ladle of batter into the center. Quickly swirl the kadhai to spread the batter thinly on the walls. What has not stuck to the walls of the kadhai should pool in the bottom (Appams should look like a bowl with thick bottom!).
Cover the kadhai and cook for 3-4 minutes or until the Appam is golden and crispy on its thin edges and cooked and fluffy at the bottom.
Gently run a spatula under the Appam to release it from the kadhai and serve hot in a small basket.