Soak chilies and garlic: Soak dried red chilies and garlic in hot water for 20 minutes, then drain.
Blend red lasun chutney: Blend soaked chilies and garlic with thin sev and just enough soaking water until completely smooth and thick. Set aside.
For Green Chutney
Blend green chaat chutney: Blend cilantro, green chilies, lemon juice, salt, thin sev, and ice cubes until smooth and bright green. Adjust salt and spice to taste. Set aside.
Assemble the Sev Puri
Set up assembly station: Arrange papdi on a large platter. Keep diced potatoes, onions, tomatoes, and raw mango in separate bowls. Transfer chutneys to squeeze bottles.
Assemble: Place a small spoonful of diced potatoes on each puri. Sprinkle with chaat masala and red chili powder. Top with onions and tomatoes.
Add chutneys: Drizzle red lasun chutney, green chutney, and tamarind chutney over each puri.
Garnish: Shower with thin sev, raw mango pieces, masala chana dal or boondi, and chopped cilantro.
Serve immediately: Assemble and serve one by one to keep puris crispy.