Marinated in spiced yoghurt, Kashmiri chillies, and garlic, then roasted over roaring tandoor charcoal embers with charred edges.
Pressure-cook the soaked kidney beans until completely soft; drain well.
Mash the beans and potato together until mostly smooth.
Add onion, green chilies, ginger, toasted gram flour, garam masala, chaat masala, and salt; knead well.
Form into round patties and chill 20 minutes.
Shallow-fry in a little oil over medium-high heat until crisp and golden on both sides.
Serve hot with mint chutney and onion slices.