The Mint Chutney recipe from indianfoodforever works really well. A "bunch" of mint turns out to be around 1 cup loosely packed leaves to balance out a spice green chili; less for a less spicy pepper -- I used a homegrown thai pepper, and it... took a lot of mint. I also added in a tablespoon or two of lime juice. Tamarinds are available in the "tropical fruits" bin at Harris Teeter, Whole Foods, and almost any Latin American or Indian grocery; the paste tastes sulphur-y (like Molasses), the soak method below really does work!

1 bunch fresh mint leaves, chopped
2 green chillies, finely diced
2 tbsp tamarind pulp with water (see below)
1 tbsp lime juice
Salt To Taste

* To make tamarind pulp soak tamarind seeds (remove the brittle shell and the veins) in water and keep aside for 2 hours; extract the seeds and seed-casing skin with a spoon.
* Grind (blend) it to a smooth paste with green chillies, lime, salt and tamarind juice.