Soak rice for 3 hrs minimum. Cut and peel tapioca.
Chop them into small cubes or you can even grate it.
Add red chilli, pepper, cumin seeds and cut tapioca to the blender.
Grind it with little water. Transfer to the mixing bowl.
Drain water from soaked rice and grind it with little water.
It can be ground coarsely (finer than rava) or smooth too. Add to the mixing bowl.
Add salt, finely chopped onion and curry leaves. Mix well. Adjust the consistency of the batter, it should be thick like adai batter.
Heat a tawa and drizzle with oil. Spread a ladle full of batter and cook covered in medium flame. Flip and cook for a minute.