Cut yam into thick
slices and parboil them in plenty of water in a deep no-stick pan. (Or steam them in a steamer or cook under pressure till 1 whistle is given out.)
Drain water off in a
colander and keep the yam aside.
Heat mustard oil in
another deep non-stick pan, add cumin seeds and asafoetida and let the seeds change colour.
Add gram flour, mix
and saute, on medium heat, for a few minutes or till the flour is lightly browned and fragrant.
Add turmeric powder,
red chilli powder, dried mango powder, garam masala powder and salt and mix well.
Add yam and mix till
all the pieces are well coated with the masala mixture. Cook on medium heat for 3-4 minutes, turning them and pressing each yam piece, till they are crisp on both sides.
Spread the chapattis
on the worktop, spread some mint chutney on each, place a few yam pieces on one end of each chapatti, top with a few onion slices and roll tightly.