Take 2 pieces of brinjals (medium size, green). Make incisions as shown in two or three places. (Pro tip: Making incisions in the brinjals not only speeds up the cooking process but also allows you to check whether there are any insects inside them.)
Brush a little bit of cooking oil on the surface of the two brinjals.
Now, turn on your gas stove, put an iron stand and roast the two brinjals directly on a medium flame. Turn them periodically to cook them nicely on all sides. Alternatively, you can grease an iron tawa with oil and roast the brinjals on it.
When the brinjals are roasted nicely, remove them on a plate, let it cool down a bit and peel off the skin from them. Then cut the stem from both.
Put the peeled roasted brinjals in a bowl and mash them with a vegetable masher or the backside of a stainless-steel glass. It should be a fine paste as shown in the image below without any larger piece in it. Keep it aside.
Now, heat 1 tsp of cooking oil in a kadai or a pan on a medium flame and put 5 pieces of green chilies (whole, without stalk) and 20 pieces of garlic (deskinned, whole) in it when it is hot. Stir and fry them for about a minute or so. Then, add a portion of the ¼ cup of raw peanuts you have to it. Stir continuously and fry them for another minute or so.
When done, transfer it to a mortar and pestle. Crush it to a coarse paste. Keep it aside.
Now, in the same kadai, heat 4 tbsp of cooking oil on a medium flame. When it is hot, put ½ tsp of cumin seeds, ½ tsp of mustard seeds and the rest of the raw peanuts and fry them for about half a minute or so.
Now, add ½ cup of onions (finely chopped) in it. Stir and fry them for about a couple of minutes until the onions start to turn golden brown in color.
When they do, add the chili, garlic and peanut paste to it. Stir continuously and fry it for another minute or so.
Now, add the lower white part of the 1 cup finely chopped spring onion to it. Fry for another minute or so. (Pro tip: Always cook the lower part of the spring onions separately, otherwise it will render a raw taste).
Now, add the mashed roasted brinjal and salt to taste. Mix them all nicely with the other ingredients in the kadai. Turn the flame of the gas stove to high and stir it continuously to fry them all nicely for about a minute or so. (Pro tip: Stirring continuously is recommended to ensure that the baingan bharta does not stick at the bottom and burn. You need not fry it for a long time as everything is partially cooked already).
Now, add the finely chopped green part of the spring onions. Mix everything nicely and cook it for another two minutes, now on a low flame. (Pro tip: The generous amount of spring onions will play an important role in enhancing the taste of the baingan bharta).
Finally, add ½ cup of finely chopped coriander leaves to it.
Mix them nicely and check the baingan bharta. Finally, turn off the gas stove.
In the end, add 1 tbsp of lemon juice (half of a standard size lemon) to it for an additional sour taste. Mix it.
Your homemade tasty baingan bharta is ready. Serve it with a little bit of mango pickle, onions and green chilies along with hot roti of any kind.