Salsa Verde con Aguacate (Green Sauce with Avocado)

In a food processor, blender or heavy mortar, process or pound the garlic and salt to a paste. Add the onion, chilies and tomatillos; either pulse in the processor to a slightly chunky purée or pound and mash the ingredients together as fine as possible. For a smooth machine-finished purée, add the avocado and the cilantro and process. If using the hand method, chop the avocado fine and mash it into the onion-tomatillo mixture; chop the cilantro leaves and stir in. Or for a compromise version, pour the machine-processed onion-tomatillo mixture into a bowl and mix in the hand-chopped avocado along with the cilantro. Serve as soon as possible, certainly within 1 hour.