Mix the cooking Soda into the sour curds. The Curds will foam up.
Pound the Ginger and Green Chilli into a soft paste.
Mix the Ginger Chilli Paste, Semiya(Vermicelli), Sooji, Salt and water into the foaming Curds. Leave aside for at least 30 minutes. The batter will rise and Semiya will become soft.
Heat the oil and fry the Onion, Zeera and Curry Leaves for a minute. Mix this into the batter
Heat the Pan. Put the batter onto the pan with a ladle, and tap the pan to spread the batter.
Pour a little oil along the edges of the Uthappam and roast on a medium flame. When it is done on one side, flip it over, and let it cook on the other side also. Serve hot with any Chutney of your choice, or with Sambar.