I figured I'd share it with y'all, with Keith's blessing.
I've edited it here a little bit, which seems fair, as it's apparently been edited by nearly every pair of hands it's passed through thus far.
All quantities are very approximate:Keith insisted that the top line, the one that I bolded and italicized, was the most important one on the list. In fact, I seem to remember (but don't quote me on this) that Keith didn't actually use pequins at all, but substituted extra serranos instead.
Tomatilloes: 8 to 16 depending on size.
Chiles: 2 Serranos + 2 Jalapeños + 8 Pequins + 2 Anaheims.
More or less to taste. I typically use the serranos and jalapeños green and the pequins red. Feel free to use different varieties of chiles as dictated by taste/availability.
Garlic: 4 cloves
Onion: 1 really small onion, or half a medium onion.
Roast above ingredients in a cast iron pan, oil-free, turning occasionally. Leave husks on tomatillos while you roast 'em. The husks will be nicely blackened, the skins translucent, and the fruits soft when they're done. [Let me add: the goal is to blacken the skin while doing the least tomatillo-exploding that you can. That way they don't lose juice into the pan, that burns and smells sometimes. That means moving them around the pan as they roast.]
Put roasted vegetables in food processor with:
Salt: 1/2 Teaspoon
Cilantro: 1/4 Cup
...and process briefly.
Transfer to a pot, and cook the mixture for 5 minutes. [This darkens it up a bit, and mellows the flavors. It tastes too raw otherwise.]
I admit, after reading this recipe, that I have questions. Pan-roasting big, bulky vegetables can be a hit-or-miss proposition, after all, especially when your chile peppers are as wrinkly as Anaheims are; you can wind up with the parts getting blackened that were in direct contact with the pan, but the rest of the vegetable undercooked.
And we assume that we eventually take the husks off the tomatillos. And then there's the question of whether you skin, seed and de-vein the Anaheims, or just throw them in the blender and hope for the best.
Nevertheless, I get the feeling that this is one of those recipes that's hard to mess up.
And I think that Keith must have quadrupled the batch or something; because there was no way that 8 to 16 tomatillos could have produced that much salsa. So doubling, tripling, or quadrupling this recipe is apparently doable, and is highly recommended.
And one more benefit of this recipe, is that it gives me one more bit of rhetorical leverage when arguing with my wife about getting a cast-iron skillet. :-)