Take besan in a bowl. Add yogurt and mix well. Add water and whisk till smooth. Keep it overnight to ferment.
Dry roast the rice and dal on medium heat for four to five minutes. Cool and grind into a semi-coarse powder. Put the powder in a bowl.
Add yogurt and one and a half cups of warm water. Mix thoroughly so that no lumps are formed and the batter is of pouring consistency. Let it ferment overnight.
Add green chilli-ginger paste, salt and turmeric powder to the besan mixture and mix well. Add salt, crushed black peppercorns and green chilli paste to the rice batter and mix well.
Mix soda and lemon juice in a small bowl. Add half of it to the white batter and the remaining to the besan batter.Heat water in a steamer and grease the dhokla plates. Pour white batter into two plates till half full and fit the plates into the stand.
Keep the stand in the steamer, cover with the lid and steam till half done.Take the stand out and remove the dhokla plates. Spread green chutney evenly on both the white dhoklas. Pour the besan batter over this and rotate the plates so that the batter spreads evenly.
Fit the plates into the stand and place the stand in the steamer. Close the lid and steam for eight minutes. Take the stand out and let it cool slightly. Garnish with coriander leaves and coconut. Or you can pour a tempering of oil and mustard seeds.
Cut into squares and serve.