Instead of using oven, brinjal can also be done in stovetop or microwave the brinjals for 4 - 10 minutes till the skin shrinks (Depends on the microwave temperature, mine is 700 watt and it took 7 minutes. Keep an eye after 5 minutes)
Small brinjal can be used of big eggplant in that case cooking time may vary
Green Chilli and Chilli Powder combo can be used for extra spicy version
Can crackle Cumin seeds, in that case skip Cumin powder
Adjust the water quantity according to the consistency you desire your gravy