Add cumin seeds, coriander seeds, fennel seeds, dried red chilies, and black peppercorns to a pan and dry roast on a low flame until aromatic, stirring frequently.
Cool the spices for 5 minutes, then grind them with black salt, chaat masala, and regular salt to a coarse powder. From this roasted powder, use 2 teaspoons in the recipe and store the remaining spice mix in an airtight jar at room temperature for upto a month.
Make The Chaat
In a wide bowl, add boiled potatoes and cooked chana. Lightly mash together with fingers or a fork so they start to bind but still retain texture.
Add onions, green chilies, and most of the coriander (reserve a little for garnish). Mix gently.
Season with 2 teaspoon bhaja masala.
Pour in tamarind chutney and green chutney. Mix using your fingers, lightly squeezing so the potatoes absorb the spices and chutneys; adjust tang, salt, and heat. Add a splash of water if the mixture looks very thick.
Just before serving, crush puchka shells with your hands directly into the bowl, into small shards (not powder). Toss quickly so the shells get coated, but do not mix for too long or they will turn soggy.
Transfer the churmur to a Donna (dried-leaves bowl) or small bowls. Finish with a generous squeeze of lemon, a final sprinkle of bhaja masala, and chopped cilantro on top. For extra crunch, top with a little sev, crushed golgappe, and pomegranate seeds and serve immediately.
Notes
Using warm boiled potatoes with room-temperature chutneys gives that slightly steamy chaat feel you get on the street.You can replace black chana with ragda for a change.Texture balance: Aim for 60–70% soft (potato + chana), 30–40% crisp (puchka + optional sev) so it doesn’t collapse into a paste.You can add a few drops of raw mustard oil at the end, which adds typical Bengali street-food pungency (like jhalmuri).