In a mixing bowl, add vada flour. Add buttermilk gradually and make knead the dough.
Then spread the vada dough and add 1 tbsp sour curd on its upper surface.
Now cover the dough and rest it for at least 6 hours or overnight for fermentation.
Then in a pan, add coriander seeds, fennel seeds, cumin seeds, and black pepper. Roast for 2 minutes and in a mortal-pestle crush it into a coarse powder. Special masala is ready
After resting time, the dough is slightly soft and becomes frothy.
Now add salt, green chili paste, ginger paste, coarsely ground masala, turmeric powder, hing, white sesame seeds, and coriander leaves. Mix well.
Then add 1 tbsp hot oil and mix well. You can add a pinch of baking soda if your vada is not puffed up while frying.
Now, grease your palm with water and make round disc shape vada. You can also make vada on wet cotton cloth.
Heat oil in a pan, add vada and deep-fried on medium-low flame.
Take out fried vada on a wire rack or tissue paper and serve with green chutney.