Place the halved tomatillos and the whole garlic clove in the large skillet lined with foil. Set the skillet over medium heat and and dry roast for about 3 to 4 minutes per side. The tomatillos should be soft and blotchy and the garlic will be browned. Transfer the roasted tomatillos and garlic to the blender.

Dry roast the jalapeños in the skillet, until the skin blisters. Remove the the heat and slice down the middle, removing the seeds and membrane. Add to the blender along with the avocado chunks and cilantro. Blend until you have a smooth consistency. Taste and add lime juice if desired and blend again. Pour into a serving bowl.

Rinse the chopped onion and stir into the salsa. Add salt to taste and serve. Makes about 4 cups of salsa.