Mash the sweet potatoes in a bowl and then add the chickpea flour, garam masala, ginger, salt, cilantro, and yogurt. Mix well and then form into small patties about 2-inches in diameter.
Heat the oil in a large nonstick skillet over medium-high heat and cook the patties in batches so they have plenty of room to fry. Cook for about 2 minutes on each side, or until they are golden and crispy and cooked through.
Place the juice, onion, cilantro, chat masala, and salt in a food processor and process to a paste. Add the mango and pulse until the chunks are coarsely chopped. Chill until ready to serve.