Rinse the chana 2–3 times in water, then soak them overnight or for at least 8 hours.
After soaking, drain the chickpeas and set them aside.
In a pressure cooker, add the soaked chana and cubed potatoes along with 4 cups of water and salt.
Pressure cook on medium heat for 4–5 whistles, then allow the pressure to release naturally.
Heat oil in a pan over medium flame.
Add the chopped onions and sauté for about a minute, then add the chopped tomatoes and cook until soft.
Add the cumin powder, red chili powder, coriander powder, turmeric powder, chaat masala, chole masala, and salt. Stir well and cook the masala mixture for 1–2 minutes until aromatic.
Add the ginger-garlic paste and 1/2 cup of water. Mix well, cover the pan, and simmer the masala on low heat for 10 minutes.
Open the pressure cooker and remove the boiled potatoes. Lightly mash them using a masher.
Add the boiled chickpeas to the prepared masala gravy, mix well, and simmer for 5–7 minutes.
Add the mashed potatoes to the curry, stir to combine, then add the tamarind pulp and cook for another 10 minutes on medium heat.
Garnish the Chana Masala with chopped green chilies and mint leaves. Optionally, you can also add fresh coriander leaves before turning off the heat.
Serve hot with naan, poori, or rice.