How to Make It
Bring a large pot of water to a boil over high. Add tomatillos, and return to a boil; cook until softened, about 4 minutes. Drain well, and let cool 10 minutes. Transfer to a food processor. Add chiles, cilantro, onion, lime juice, garlic, salt, and agave, and process until mostly smooth, about 30 seconds. Refrigerate in an airtight container up to 2 weeks.