Heat oil in a pan and add the mustard seeds and when they splutter, add chana dal and fry for few seconds. Add urad dal and cumin seeds next and fry for few seconds till they brown a bit. Ensure that the tadka is not overly browned as we do not want to see blackened tadka bits in the dish, we want to see the natural colors of eggplant!. Quickly add curry leaves and hing and sauté for a few seconds and then add chopped onion, green chilies and garlic and fry for 3 to 4 mins.