Meanwhile, make the green curry: in a saute pan, sweat the onion in the remaining olive oil over very gentle heat. When, after about 10 minutes, it starts to soften and become translucent ...
Add the garlic (if using) and curry leaves and cook for 10 seconds before adding the tomatoes. Cook for 7 minutes. Add the sugar and cook for a minute before adding back in the cooked eggplant.