Grease an 8 x 4 inch tray with some oil and set it aside. Bring 3.5 cups of water to boil in a wide pan on medium heat.
In a large bowl, transfer the chopped coriander leaves, add the spices, 2 tsp sesame seeds, salt, and sugar.
Add crushed ginger, garlic, chillies, and some yogurt. Mix everything well to release all the juices.
Transfer the chickpea flour and rice flour. Mix everything well.
Add little water at a time to form a lump-free thick batter. I used around ⅓ cup water - do not make the batter very runny.
Transfer the batter to the greased tray, spread it evenly, and sprinkle generous amounts of sesame seeds. Press them a little with a spatula.
Keep a trivet in the pot of boiling water, place the tray, and cover the pan with a lid. Steam the batter for about 16-18 mins on medium heat or until the cake comes out clean when a toothpick is inserted in the middle.
Turn off the heat, transfer the pan to a cooling rack for about 45 minutes. Run a butter knife around the corners and flip it on a cutting board.
Cut the cake into any desired shape or 18 equal pieces.
Heat around 2 tbsp oil in a pan on medium high heat. Lower the temperature to medium and place all the kothimbir vadi keeping some space in between them.
Divide 1 tbsp oil by drizzling on the top of each vadi.
Cook the vadi for about 3 minutes. Carefully turn each vadi with the help of a tong and cook the other side for about 3 minutes.
Lower the heat to medium low, fip each vadi carefully, and cook for about 3-4 minutes until crispy. Serve them hot or warm.