Add cilantro, oil, rice flour, garlic, green chilies, turmeric, besan, salt and water to a medium bowl. Mix well.
Add 1½ cups water to the Instant Pot insert. Set on Sauté mode so the water starts to heat. Note: Heating up the water before placing the batter in the Instant Pot will result in light cakes. Make sure to do this about 5 minutes before you are ready place the batter in the Instant Pot for steaming. Boiling it for too long may cause a lot if water to evaporate.
Grease a 7½ inch stainless steel bowl with cooking oil or spray.
Add baking soda to the batter and mix well. Quickly pour the batter in the greased bowl. Place the bowl on the instant pot trivet and carefully place the trivet inside the Instant Pot. Note: It is important to start the steaming process within couple of minutes for the baking soda to work. Close Instant Pot lid with pressure valve to venting.
Set Instant Pot to Steam mode, with an external timer for 12 minutes. Note: Timer function does not work with Steam/Venting, so an external timer is needed.
Once the timer goes off, Press Cancel and open the Instant Pot after 5 minutes.
Carefuly take out the bowl. Cut into small square pieces.
Heat a nonstick pan with half of the oil for pan frying. Spread half of the sesame seeds and then line the Kothimbir Vadi on the pan. Cook on medium heat for 2 to 3 minutes. Then sprinkle remaining oil and sesame seeds on top and carefully flip the Vadi. Cook the other side for 2 to 3 minutes or until crispy. Serve hot.