Blend the pomegranate with two cups water and set aside the juice after straining.
Blend cilantro, mint, black salt, cumin powder, lemon juice, chaat masala, pain puri masala to a coarse texture. Add half cup water and blend to a nearly smooth puree. Add this to the pomegranate juice. This is the pani to fill the puri.
To make the potato filling: Add the spices listed under pottao filling to the cubed mashed potatoes. combine thoroughyl. Set aside.
To assemble: Poke a hole in the puri. Add half a teaspoon of potato mixture, a couple of garbanzos, some sprouts, onions, and top with sev, pomegranate and cilantro. Repeat with the rest of the puris. Pour about 3 tablespoons of pomegranate pani to fill the puri.
Serve immediately