Soak the chickpeas overnight and simmer for 1 ½ to 2 hours to get the desired tenderness.
Cut potato into small cubes and bring to boil.
In a large bowl add cooked chickpeas (chana) and boiled potato cubes. Then season with red chili powder, crushed cumin seeds, salt and chaat masala. Mix well.
Pour in green chatney, tamarind pulp and yogurt mixed with water. Mix again.
Lastly, add sliced onion, tomato and fresh coriander leaves. Mix yet again and your chaat is ready to be served.