Soak all the lentils and rice overnight with enough water.
Blend with minimum water & salt to get a thick batter,keep it aside for 6 hrs/overnight.
Add ginger,chillies and baking soda to the batter.
Steam for 15-20 mins in an oiled vessel.
Let it cool and cut into pieces.
In a pan ,heat oil and temper curry leaves,mustard and chillies and add the dhokla pieces to tempering.
Garnish with fresh coriander.