In a pan, heat 2 tablespoons of oil over medium heat. Add mustard seeds and cumin seeds, allowing them to crackle. Add chopped green chilies, ginger, garlic, and curry leaves. Sauté until fragrant. Stir in the chopped onion and cook until translucent.

Add turmeric powder, red chili powder, and asafoetida to the pan. Mix well and add the boiled and mashed potatoes. Season with salt and mix thoroughly to combine all the flavors. Cook for 3-4 minutes, then add chopped cilantro. Set the potato mixture aside to cool.

Once cooled, shape the potato mixture into round, medium-sized balls (about the size of a golf ball). This forms the base of your vada filling. Ensure they are firm enough to hold their shape when frying.

To prepare the batter, take a large bowl and combine gram flour, turmeric, red chili powder, and salt. Gradually add water, whisking continuously to form a thick, smooth batter. Add a pinch of baking soda to make the batter slightly airy.

Heat oil in a deep pan over medium heat. Dip each potato ball into the batter, coating it evenly, and carefully lower it into the hot oil. Fry in batches until golden and crisp on all sides. Remove with a slotted spoon and place on paper towels to drain excess oil.

For the assembly, slit the pav buns horizontally, keeping them connected at the back. Lightly toast the buns on a hot skillet with a little butter until they are warm and slightly crisp.

Spread a layer of green chutney on one side of the pav and tamarind chutney on the other. Place a fried vada in each bun. Sprinkle a bit of dry garlic chutney (optional) for an authentic street-style touch.

Serve the Vada Pav hot, accompanied by extra chutneys or a few fried green chilies on the side for those who love a spicy kick. The combination of the spicy, tangy chutneys with the crispy vada and soft pav buns makes this a quintessential Indian street food experience.