Recipe can be found@ Zesty South Indian Kitchen
Soak the raw rice for 6 hours or overnight.
Grind all ingredients expect salt, sugar and yeast into a fine paste. When the batter slightly coarsely ground remove 2 tablespoon of batter and set aside. Then continue grinding until you get fine paste.
In a small sauce pan add coarsely ground batter plus ½ cup of water and heat it until the mixture become thick and cooked well. Set aside for cooling. Once it is cooled add back to appam batter. To this add yeast, sugar and set aside for fermentation about 8 hours.
When you are ready to make the appam add salt and set aside for 5 minutes.
Heat appachatti/appam pan over medium low heat, you can test whether pan is ready by a adding a drop of water and it sizzles immediately then it is ready to make pancake. Then pour a ladle of batter into the pan. Lightly swirl the pan so that batter gets coated all over and form the shape of round pancake however center part is slightly thick compared to sides. Cook the pancakes on 1 side until they are set by covering with lid, until crisp on the sides and cooked in the center. Transfer pancakes to a plate while you make the rest.
Enjoy with any spicy curry.