Preheat the broiler: Set the rack about 6 inches from the heating element.
Prep the tomatillos: Remove the papery husks from the tomatillos and rinse well. Cut the tomatillos in half and place cut side down on a foil-lined baking sheet. Add a few garlic cloves in their skin (if using). Place under a broiler for about 5-7 minutes to lightly blacken the skins of the tomatillos.
Combine the cooked tomatillos and seasonings, then pulse in a blender: Place the cooked tomatillos, lime juice, onions, garlic (if using), cilantro, chili peppers in a blender or food processor and pulse until all ingredients are finely chopped and mixed.
Season and serve: Season with salt to taste. Cool, then refrigerate. Serve with chips or as a salsa accompaniment to Mexican dishes.
