Chop the eggplant into very tiny pieces. Heat oil, add mustard seeds, when popping add curry leaves, chillies, onions and fry till onions become translucent. Add tomatoes and eggplant and fry for another five minutes. If using tamarind paste add a cup and half of water, or pour equal quantity of extract from fresh pulp. Throw in the turmeric, salt and garlic. Let it simmer for a while until eggplant becomes really soft and is barely able to retain its shape. Remove from heat.
Tomato-Onion Gotsu: More tomatoes can be substituted instead of the eggplant for a tomato- onion gotsu. Add more chillies if necessary.