Soak tamarind pulp in water overnight. The next day, mash the pulp into the water & blend throughly. Strain liquid in a sieve or through some cheesecloth & discard the fibres. Stir in the remaining ingredients except the mint leaves. Whisk thoroughly until the sugar has dissolved. Sprinkle with mint & serve chilled. Serve with samosas or other salty (*chaat*) dishes.