Heat oil and crackle mustard seeds and urad dal.
when it pops, add bittergourd, potatoes, garlic, salt and turmeric powder. Mix well.
sprinkle little water, close cook for 5 minutes.
open and add sliced onions, chilli powder and mix well.
fry in simmer until roasted. keep stirring in between.
lastly, add jaggery water and give it a mix.
serve hot with rice and curry.