Make sure the potatoes are boiled in salted water and peeled.
In a sauté pan on medium heat add the oil, mustard seeds, and let them fry until they start popping, add the curry leaves, garlic, ginger, green chili and cook for a minute.
Break up the potato in your hand into the pan and add turmeric powder, fresh coriander leaves, lime juice and season with salt. Cook until the mixture is dry and the potatoes have taken on the flavors of the masala.
Set the sauté pan aside and place a heavy bottom sauce pot on the same stove, pour in vegetable oil half way through and let it heat up gently.
In a medium mixing bowl add the gram flour, corn starch, turmeric powder, chili power, salt and stir. Add the baking soda, water and stir with a whisk to remove any lumps. Set aside.
The potato mixture should’ve cooled down enough to handle it with your hands. Divide the mixture into 10 portions and roll into balls. Test the heat of the oil with a little dust of flour, if it sizzles and dissolves, then its hot enough.
Dunk the potato dumpling into the batter and deep fry, I prefer using my hands but you can use a fork/slotted spoon. Deep fry for 2-3 minutes until golden and the vada rises to the top.
Transfer to kitchen paper towel to drain out the excess oil. Repeat until all are done. Deepening on how large your sauce pot it you will be able to fry a few and one go.
The fried batata Vadas should be served in a pav (soft dinner roll) with green chutney, garlic chutney and tamarind chutney, serve with a fried green.