Heat oil in a large saucepan over medium-high heat; add coriander seeds and chile; toast until the coriander turns reddish brown and the chile is slightly blackened, about 30 seconds. With a slotted spoon, transfer spices to a plate to cool. Grind in spice grinder or mortar and pestle until the mixture is the texture of coarsely ground black pepper.

Dissolve tamarind concentrate (or lime juice) in water. Reheat the oil over medium-high heat; add mustard seeds. When the seeds begin to pop, cover the pan. As soon as the popping stops, add eggplant and shallots; cook, stirring constantly, for 1 minute. Add the tamarind (or lime juice) mixture, salt and the ground spices; bring to a boil. Reduce heat to medium-low, cover and simmer until the eggplant is fork-tender, 3 to 5 minutes. Coarsely mash the stew with a potato masher. Sprinkle with cilantro and serve.