Boil potatoes until completely cooked. Peel and mash them while still warm. Set aside and let them cool slightly.
Heat 2 tablespoons oil in a kadhai or pan over medium heat. Add mustard seeds and let them crackle.
Add cumin seeds, curry leaves, and chopped green chillies. Saute for 10to15 seconds until fragrant.
Add turmeric powder and immediately add the mashed potatoes. Mix everything well so the spices coat the potatoes evenly.
Add salt, coriander leaves, and lemon juice. Mix well and cook for 2 minutes on low heat. Turn off the heat and let the mixture cool completely.
Once cooled, divide the potato mixture into 6 equal portions and shape them into smooth round balls. Keep them covered.
Make the Batter
In a mixing bowl, add besan, turmeric powder, red chilli powder, salt, and baking soda. Mix the dry ingredients well.
Add water gradually and whisk to make a smooth batter with no lumps. The consistency should be thick enough to coat the back of a spoon but still flowing.
Add 1 tablespoon of hot oil to the batter and mix well. This makes the coating crispy. Let the batter rest for 5 minutes.
Fry the Vadas
Heat oil for deep frying in a kadhai or deep pan. The oil should be medium hot, about 180°C. Test by dropping a small amount of batter. It should sizzle and rise slowly.
Take one potato ball, dip it completely in the batter so it is coated evenly from all sides, and gently slide it into the hot oil.
Fry 2to3 vadas at a time without overcrowding. Fry on medium to high heat, turning occasionally, until the vadas are golden brown and crispy all over. This takes about 4to5 minutes per batch.
Remove the vadas with a slotted spoon and drain on paper towels. Keep them warm.
In the same oil, fry the whole green chillies for 30to40 seconds until they blister. Remove and drain.
Assemble the Vada Pav
Slice each pav horizontally but do not cut all the way through. Keep one side attached like a hinge.
Spread garlic chutney on one side of the pav and green chutney on the other side. Add a drizzle of tamarind chutney if using.
Place one hot vada inside the pav and press gently. Serve immediately with fried green chillies and peanuts on the side.
Notes
Equipment - You need a kadhai or deep frying pan, a mixing bowl, and a potato masher. A slotted spoon makes removing vadas easier.Make ahead - You can prepare the potato filling and store it in the fridge for up to 24 hours. Shape the balls just before frying. The batter is best made fresh but can be stored for 2to3 hours at room temperature.Oil temperature - Maintaining the right oil temperature is critical. If unsure, use a kitchen thermometer and keep it between 170 to 180°C.Garlic chutney - Grind 6 to 8 garlic cloves with 1 teaspoon red chilli powder, 1/2 teaspoon salt, and 1 tablespoon water. Store in the fridge for up to a week.Vegan option - This recipe is already vegan if you skip the butter for toasting pav or use vegan butter.Gluten note - The vada itself is gluten free, but regular pav contains gluten. Use gluten free rolls if needed.Leftover storage - Store vadas separately from pav. Refrigerate vadas for up to 2 days and reheat in an oven at 180°C for 8 to 10 minutes to restore crispiness.