I finally got Ashok to show me this one today...
To start it off, I poured boiling hot water (1.5L to 2L) over a chunk of dried tamarind (1 package) and let it sit overnight to soften up.
Today we squished the tamarind pulp with our hands so that it would dissolve well into the water. I'm sure a blender would be handy here. Then we strained the liquid into a pot and started heating it up.
Added a bunch of sugar... probably between 1 to 1.5 cups... 4 to 5 tablespoons of salt, 3 or 4 tablespoons of chaat masala, 2 to 3 tablespoons of cayenne (spice to taste), 2 to 3 tablespoons of crushed toasted cumin seeds (to taste), and a small bunch of minced mint leaves. He said we could also add some black salt, but we didn't have any on hand.
We brought the mixture to a boil, then added some corn starch to thicken it up. Simmered for 30 seconds longer, then removed it from the heat.
As a final touch he added some thinly sliced over-ripe bananas. He said you can also add raisins and/ or halved mushy grapes.