Mix the rice, wheat, soya and nachni flours with the buttermilk to make a smooth batter. Add the salt, fresh coriander and green chillies and mix well. Let the batter rest for about fifteen minutes.
Heat a non-stick pan. Put two drops of oil and wipe the tawa clean with a wet muslin cloth. Add a tablespoon of oil to the tawa and pour half a ladleful of batter and spread it to a thin three inch round.
Drizzle a little oil all around. When the underside is done, flip and fry the other side similarly. Serve hot with tomato ketchup.