Step 1 Bring a large pot of water to boil. Add the tomatillos and boil just until they darken to an olive shade, about 5 minutes. Remove from heat, drain and set aside until cool enough to handle.
Step 2 In a food processor, combine the boiled tomatillos with the onion, chiles, cilantro and salt. Pulse until the ingredients are blended to form a salsa. This makes a generous 6 cups of salsa, which can be covered and refrigerated until ready to use, up to 1 week.