First, you have to take 1 cup of kala chana (black chickpeas) in a bowl. Rinse them twice or thrice in clear water. Then soak them for 7 to 8 hours with 1-2 inches above the chickpeas.
Later, drain all the water.
Take a pressure cooker and transfer the chickpeas with salt to taste into it. Then add enough water to cover the chickpeas properly- about 1 cup.
After that, close the cooker lid and wait for 6 to 7 whistles on high heat.
Now, finely chop all the vegetables.
When the pressure comes down, naturally open the cooker lid. Drain the water and transfer the chickpeas to a mixing bowl. If the chana are not done, then again for a few minutes.
Now add chopped tomato, onion, green chili, and coriander leaves.
Now add 1/4 tsp of chaat masala powder.
Toss all of these ingredients well and squeeze lemon on it.
Now, again, toss everything well. The kala chana chaat is ready. Serve it as a snack or meal. You can pack it for lunch box also.