Heat the oil in a large pot over high heat. Add the onion and garlic and cook for 2 minutes. Lower the heat and add all the other ingredients to the pot. Cover and simmer for 30 minutes.
After 30 minutes, remove the lid. If there is still a lot of liquid, continue cooking for another 30 minutes uncovered. If the amount of liquid looks right, put back the lid and cook for 30 more minutes.
My children are not very fond of the eggplant skin, so sometimes I peel them for this dish.