soak chana dal for 30 min to 1 hour. drain and add to the pan along with yam and raw banana.
further add green chilli, curry leaves, salt and turmeric powder. close and cook until soft.
grind coconut and cumin to a fine paste. add it to the cooked vegetable.
mix well and let it boil. add jaggery and pepper powder. mix again.
for tempering: heat coconut oil and crackle mustard seeds, red chilli, curry leaves and grated coconut.
fry until reddish brown and add the tempering to the curry. mix well.