1 whole jalapeño (you will only use 1/4–1/2 in the dressing!)
1 clove garlic (optional: for a little added sweetness use a roasted clove)
Peel the tomatillos and rinse off the sticky outer coating. Place them in a pot of boiling water and boil for five minutes. Remove them and let cool.
While the tomatillos are boiling, juice the lime by cutting it in half and squeezing the juice from both halves into a food processor bowl. Cut the jalapeño in half lengthwise ( if you want the dressing to be on the milder side, de-seed the half and cut it in half again and only use the quarter with no seeds). Remove the seeds and set aside, roughly chop/slice the pepper. Put the pepper into the food processor with about 1/2 tsp of the seeds ( the seeds are what actually make jalapeño spicy, so be as liberal or conservative as your taste desires).
Roughly chop the garlic and add to the food processor with the avocado, cilantro and boiled tomatillos.
Run the food processor for about two minutes or until the sauce is blended. If your sauce seems too thick, add 1 tbsp of water and blend again – continuing until it reaches your desired consistency.
Refrigerate if not using immediately. Serve on salads, nachos, tacos, fajitas, or even just with chips as a cool avocado dip!