Cook the potatoes and legumes. Boil potatoes until fork-tender, then mash while warm. Cook kala chana or white peas until soft but not mushy. Drain and set aside to cool.

Blend the green pani base. In a blender, add coriander, mint, green chilies, ginger, tamarind pulp, juice of half a lemon, black salt, roasted cumin powder, and a splash of water. Blend smooth.

Adjust and dilute. Pour the green base into a large bowl. Add 3–4 cups of ice-cold water. Stir in jaggery or sugar for balance. Taste and adjust salt, lemon, and spice. The pani should be tangy, lightly sweet, and refreshing.

Season the potato filling. In a bowl, mix mashed potatoes with 1 teaspoon roasted cumin powder, 1/2 teaspoon black salt, a pinch of regular salt, a squeeze of lemon, and a touch of red chili powder or chaat masala if you like. Fold in a spoonful of tamarind pulp for the signature Kolkata tang.

Season the legumes. Toss the cooked chana or peas with a pinch of black salt, roasted cumin, and lemon. Keep them separate from the potato mix for better texture.

Chill the pani. Refrigerate the pani for at least 30 minutes. Cold pani keeps puris crisp longer and boosts flavor.

Prep the puris. Gently tap a hole at the top center of each puri with your thumb. Be careful to avoid cracks along the sides.

Assemble just before serving. Add 1 teaspoon of potato filling to each puri. Top with a few chana or peas. Spoon in a little chopped onion if using.

Add the pani. Dip each filled puri into the cold pani, or spoon the pani in until nearly full. Eat immediately.

Garnish and repeat. Sprinkle a touch of sev or crushed papdi if you like extra crunch, and keep going puri by puri for the best experience.