Put the oats powder in a bowl. Add semolina, curd, salt and grated ginger to it. Mix it. If the consistency is thick, add some water. Keep it aside for half an hour.
Grease a pan, put water in the steamer, lit the stove.
Put baking soda to the batter, mix and pour it immediately to the greased bowl.
Steam it for 10-12 minutes. The best way to check if it is done properly, is to insert a knife, if it comes out clean, it is done.Keep it aside.
Make the seasoning. Heat oil in a pan, add mustard seeds, as it crackles, put sesame. Throw in the green chilly and curry leaves. Put the tempering over the prepared dhokla and cut into pieces.
Notes
You can use eno instead of baking soda. If using eno, you need to add 1.5 teaspoon of it.
You may add a little chilly powder in the seasoning.