For the masala Filling 1. * Heat the oil in a heavy based pan and add the mustard seeds, then onions, curry leaves and green chillies, and sauté over high heat till the onions are a little transparent. 2. * Add the salt and the turmeric and mix well before adding the potatoes. Turn the potatoes around till well mixed and add the water and let it simmer for 2-3 minutes.