Fill a large pot with about 8 cups (1.9 L) water. Add the potatoes and salt and bring to a boil. Cover, reduce the heat to maintain a simmer, and let the potatoes cook for 35 to 40 minutes, until they pierce easily with a fork. Drain the potatoes and let cool to room temperature. Once they are cool enough to touch, remove the skins and mash the potatoes until they are a roughly even consistency, being careful not to overmash.
While the potatoes cook, in a food processor, combine the onion, cilantro, and chiles and process until finely chopped. If you don’t have a food processor, finely chop them with a knife.
In a small bowl, stir together the chaat masala, chili powder, and 1/2 cup (50 g) of the breadcrumbs. Add the spiced breadcrumb mixture to the potatoes and mix well. Fold in the onion and herb mixture. Taste and season with more salt or spices as needed.
Divide the potato mixture into about fifteen equal-size portions. Flatten them into patties, 2 1/2 to 3 inches (6.5 to 7.5 cm) in diameter.
Get your frying station ready: Place the beaten egg in a shallow bowl and the remaining 1/2 cup (50 g) breadcrumbs on a plate next to the stove.
In a nonstick skillet, heat the oil until it begins to shimmer. Carefully brush each patty with beaten egg and then coat it in the breadcrumbs. Carefully place the patties in the skillet and cook for 3 to 4 minutes per side over medium heat until golden brown. Don’t overcrowd the pan, and fry in batches if needed, adding more oil as required. Transfer to a plate lined with a paper towel to absorb excess oil.