Start by making the batter. In a bowl, combine besan, rice flour, and a pinch of salt. Add water gradually to make a smooth, thick batter.
To make the dhokla fluffy, add a spoon of Eno or baking soda to the batter.
Grease a steaming dish or tray with a little oil. Fill a large pot or steamer with water and bring it to a boil.
Pour the prepared batter into the greased steaming dish. Place the dish inside the steamer or large pot and steam the dhokla for about 15-20 minutes.
In a separate pan, heat some oil and add mustard seeds, sesame seeds, green chilies and a pinch of sugar.
Once the dhokla is steamed, allow it to cool slightly. Then, cut it into square.
Garnish the dhokla with freshly chopped coriander and drizzle the mustard seed mix on it.