Soak the rice and the dals in water for at least 2 hours. Then grind to a fairly smooth paste in a blender. The consistency should be slightly grainy but not unlike that of a regular pancake batter, thin enough to spread on a hot griddle but thick enough to coat the back of a spoon.
Once the batter has acquired the right consistency, add to the blender the ginger, onion, cabbage, green chillies, curry leaves, chili powder, turmeric, salt. Process for about a minute or so until the cabbage and onion have broken down into small but still discernible bits. Remove the batter to a bowl and add the chopped cilantro.
Heat a griddle (cast-iron or non-stick) until drops of water spashed on it’s face sputter away immediately. Smear evenly with a thin layer of oil.
Take about 1/2 cup of batter in a rounded ladle. Pour into the center of the hot griddle, then, with a quick, concentric motion, spread the batter into a round as thinly as you can. Don’t worry if it leaves gaps. You can fill them in with drops of batter.
Pour a few drops of oil around the edges which will help crisp up the adai further.
When the underside turns golden-brown, flip the adai and cook the other side for about a minute.