To make the papdi, cut the flour tortillas into 1x2-inch pieces. Heat about half an inch of oil in a skillet set over medium-high heat and cook the tortilla pieces until deep golden. Transfer with tongs to a paper towel-lined plate as they cook, and shower with salt.
To make the mint-coriander chutney, blend the mint, coriander, jalapeño, lemon juice and a pinch of salt in a blender or food processor until well blended, scraping down the side of the bowl.
Boil the potato in a small saucepan just until tender; drain and toss with butter while it’s still warm. Toss with the chickpeas, chaat masala, and a squeeze of lime, if you like. Sprinkle with salt. Mix the yogurt, chaat masala, garlic and a pinch of salt.
To assemble, spread the papdi out on a platter or individual plates and pile on the potatoes and chickpeas, sev or Bombay mix, onion, tomato and cilantro, drop over a few small spoonfuls of the mint-coriander chutney and drizzle with the yogurt and tamarind chutney. Serve immediately.