Chop the eggplants into 1-inch cubes with the skins on. Boil eggplant pieces in large stockpot for about 5-7 minutes, or until soft. Drain well, set aside.
Heat oil in a large pan over medium heat. Mix in cumin seeds and mustard seeds. Let them roast for about 1 minute or until they start to sizzle and pop.
Stir in onion and fry for 2 minutes or until onion is tender. Add turmeric powder and fry for another 30 seconds.
Add ginger-garlic paste, frying for about 1 minute. Stir in cayenne pepper, curry powder, and diced tomato. Cover and let simmer on low heat for about 5 minutes, or until the tomato is almost a paste (if you must, add 1-2 tablespoons of water to keep the mixture moist).
Add salt, green chiles, and plain yogurt. Cook for 30 seconds, then add the eggplants. Cover and cook for 7-10 minutes. Mix in chopped cilantro and serve over rice.