Drain the water from bengal gram dal and set it aside.
Grind together this dal, ginger and green chilli in a food processor to a coarse paste adding just a very little water.
In a bowl, mix together the coarse paste, onion, coriander, salt and mint.
Make small flat fritters with the above paste. If it is difficult to make them, add a little chickpea flour for binding.
In a wok, heat oil for deep frying. When the oil is hot, fry the fritters until brown on both sides on low medium flame.
Serve hot with chai.