Wash bittergourds and dry thoroughly.Slit open,remove seeds and cut into thin,3-cm long slices.
Mix half the chilli powder,turmeric and salt with bittergourds,and set aside for an hour.
Heat oil in a kadhai,add bittergourds and deep fry till crisp.Remove from oil,drain and set aside.
Sprinkle mustard seeds into kadhai.When they start sputtering,stir in fenugreek,green chillies,ginger and garlic,and fry for 5 minutes,stirring constantly.
Combine asafoetida and remaining chilli powder,turmeric and salt,with vinegar and mix in.Fry for a minute and remove kadhai from heat.