2 pinches salt (I use kosher, and usually have to add a little more at the end)
Boil tomatillos and peppers in water for about 10 minutes, or until the green color of the tomatillos and jalapenos turn from a slick green to a dull green (You want them to be soft, but not too mushy).
Remove tomatillos and peppers from water; cut off stem caps from peppers, but do not remove seeds (unless you're a sissy).
Place tomatillos, peppers, garlic, cilantro (if used), and a couple pinches of salt into a food processor.
Blend in the food processor for 20-30 seconds, depending upon desired consistency.
Taste the sauce, and if necessary, add more salt (pulse-mix a few times to stir in any added salt).
Pour into a re-sealable container or jar, let it rest in the fridge for about 30 minutes, then enjoy with chips or use as a condiment.
This sauce seems to keep well in the fridge for at least 10 days (I have never pushed it further than that, but then it usually doesn't last that long anyway).
NOTE: After using the food processor, it is sometimes best to open in a well ventilated area as the fumes from processing boiling hot peppers can take your breath away.
NOTE TO SISSIES: If you can't handle the heat, drinking milk and/or eating a flour tortilla will provide the best relief.