Rinse tomatillos under warm water to remove stickiness and dry them. Quarter tomatillos and in a blender puree with jalapenos, coriander, and water until very smooth. In a bowl, stir together tomatillo mixture, onion, and salt. Salsa may be made 10 hours ahead and chilled, covered. Bring salsa to room temperature before serving. Serve with tortilla chips.
Recipe courtesy of Gourmet Magazine