Ingredients
3 russet potatoes
2 tablespoons vegetable oil, plus more for deep-frying
1 teaspoon brown mustard seeds
1 teaspoon cumin seeds
1/2 teaspoon hing (asafetida)
4 fresh curry leaves
1 teaspoon ground turmeric
1/2 teaspoon Kashmiri or other red chile powder
1-inch pieces fresh ginger, peeled with a spoon and finely chopped
2 garlic cloves, minced
1/2 cup lightly packed finely chopped fresh cilantro leaves
2 teaspoons chaat masala
1 cup chickpea flour (besan)
1 teaspoon ground coriander
1 tablespoon unsalted butter
4 flaky white buns, such as potato or brioche buns
Instructions
  1. Make the vada: In a saucepan, combine the potatoes and enough water to cover by 3 inches. Bring to a boil over high heat, reduce the heat to medium, and simmer until tender, about 15 minutes. Drain, and once the potatoes are cool enough to handle, peel them using your hands (the skin should slip right off). Place the potatoes in a bowl and mash them with a fork until they are mashed but still slightly chunky.
  2. In a sauté pan, heat 2 tablespoons of oil over medium-high heat until the oil glistens. Add the mustard seeds and cumin seeds and sauté until they begin to hiss, about 2 minutes. Add the hing, curry leaves, turmeric, chile powder, ginger, and garlic. Sauté, stirring often, until the garlic is tender, about 4 minutes. Remove the pan from the heat. Season with salt and then transfer to a large bowl.
  3. Add the potatoes, cilantro, and chaat masala to the spice mixture in the bowl. Stir with a wooden spoon until everything is incorporated. Season with lime juice and salt to taste. Form the mixture into four 2-inch balls and arrange them on a plate in a single layer. Cover with a damp cloth and set aside at room temperature.
  4. In a large bowl, whisk together the chickpea flour and enough water (begin with 1/4 cup) to form a paste that resembles thick cake batter. It should not be runny. Stir in the coriander and season with salt.
  5. Line a plate with paper towels. Pour 5 inches oil into a deep heavy-bottomed pot and heat to 350°F on an instant-read thermometer. Dredge the potato balls in the chickpea batter until they are well coated. Shake to remove any excess. Using a slotted spoon, gently lower a vada into the oil and fry until golden brown on all sides, 4 to 6 minutes. Turn with the spoon as it fries to ensure even cooking and browning. Transfer to the paper towels to drain and season with salt. Repeat with the remaining vada.
  6. Assemble the chaat: In a sauté pan, melt the butter over medium heat. Split the buns and place them in the pan, interior-side down; fry until light golden brown, about 1 minute. Place one bun, open and interior sides facing up, on each of four plates. Slather both sides of the bun with green chutney, then spoon coconut chutney on top. Place a vada on the bottom bun and top with fried chiles (if using). Serve with additional chutneys on the side.