Another swipe from Epicurious.com, with tweaks :). I made this to go with the Zucchini Pancakes (below), and the pairing turned out amazingly. Would also be great as a dip for veggies/crackers/bread.
2 green cardamom pods
1/2 teaspoon black peppercorns
1 cup loosely packed fresh sprigs cilantro
2 medium garlic cloves, chopped
1 (3-inch) fresh serrano chile, including seeds, chopped -- this can be omitted if you don't like spicy things :)
2 tablespoons water
3 tablespoons olive oil
1 1/2 cups plain whole-milk yogurt
Lightly crush cardamom pods with your thumb, then remove seeds, discarding husks. Toast cardamom and peppercorns in a dry small heavy skillet over moderate heat, stirring, until fragrant and a shade darker, then cool. Grind spice mixture to a powder in grinder or mortar and pestle. Purée cilantro with spice mixture, garlic, chile, 2 tablespoons water, and 1 tablespoon oil in a blender until smooth. Stir purée into yogurt and season with salt.