Using a sharp knife, poke the eggplant in several places all around. Then massage little bit of oil on it. Also massage oil on the tomato and green chilies.
If you have a wire rack place that on the stove. You could also place the eggplant directly on the open fire. With a wire rack you can roast the eggplant and the tomato simultaneously.
Roasting tomato will take about 5 minutes, make sure to move it around to give even char all around.
As for eggplant, it will take about 15 minutes.
Also roast the green chilies in open fire or on a pan.
Soon after roasting, place everything in a big bowl and cover it for 5 minutes. The hot steam will continue softening the eggplant and the tomatoes.
Once it’s comfortable enough to handle, peel the skin off the eggplant and the tomato.
Now, instead of mashing, I prefer to place the roasted eggplant on a big chopping board and chop it for few minutes with a sharp knife.(WATCH THE VIDEO) This method keeps the eggplant fluffy and also gives even texture.
Once you have almost chopped the eggplant, sprinkle salt, add the tomato and the green chili to it and chop again.
Then add the finely chopped onion, 1 tablespoon mustard oil and cilantro to the eggplant and chop it a few more minute. Taste for salt and more if needed.
Finally give a good mix with hand and enjoy it with rice. Sprinkle little more oil if you like, chopped onion and fresh cilantro for garnish.