Soak the rice and black gram separately, at least for 6-7 hours.
Drain the rice and grind it in your processor until it becomes a paste. The texture will still feel coarse/grainy.
Pour it out into a large bowl.
Next grind the black gram. Add water only if required.
The texture of this is velvety and very smooth. Pour it into the same bowl with the rice batter. Add the yogurt/curd, salt , peppercorns and mix well. Ferment overnight.
The next day - add the sliced green chillies (or chilli paste) and oil . Mix well.
Now sprinkle the 1 tsp of fruit salt over the batter and add 2 tsp of water over it (again sprinkle it on top). You will see the bubbles forming as a reaction to the fruit salt when in contact with water.
Take a thali (plate) which you are planning to use for steaming the dhokla. I used a Cake Pan since it fits well in my rice cooker and it was the only deep plate I have on hand. Though this is not necessary, I as a precaution additionally sprinkled a little bit of Fruit salton the plate. You don't have to do it per se. Keep the steamer ready - there should not be a delay after the fruit salt is added to the batter. When its ready, pour the batter into the plate.
Once the bubbles start, very gently stir the batter for the salt to get mixed well with the batter.
Top it with the roasted seeds, powders etc. and steam for about 10 minutes
or until a knife/skewer inserted in the middle (check in multiple places) comes out clean