In a large mortar and pestle, grind together the tomatillos, garlic, and seranno chiles until almost paste-like. Alternatively, mash together in a medium-sized bowl. Add sliced avocados and mash, leaving some lumps for a chunkier texture. Add cilantro and onion and combine. Finish by adding lime juice, to taste.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.