How to Make It
If using dried chiles, heat a dry griddle or heavy skillet over moderate heat. Add half the chiles and toast, pressing down on them with a metal spatula, until they start to crackle. Turn and toast the other side. Transfer to a bowl and repeat with the remaining chiles. Cover the chiles with hot water and let soften for 30 minutes, stirring occasionally. Drain the chiles. If using canned chiles, simple wipe off the adobo.
Heat a dry griddle or heavy skillet over moderate heat. Toast the garlic, turning occasionally, until softened and blackened in spots, about 15 minutes. Let cool, then peel and roughly chop.
Meanwhile, preheat the broiler. Spread the tomatillos on a rimmed baking sheet and broil for about 8 minutes, turning once or until blackened in spots and softened. Let cool on the baking sheet.
Scrape the tomatillos and any accumulated juices into a food processor or blender and add the chiles and roasted garlic. Puree until thickened and smooth. For a chunkier salsa, pulse the tomatillos and roasted garlic until coarsely pureed; finely chop the chiles and add them to the tomatillo mixture. Transfer the salsa to a bowl and stir in 6 to 8 tablespoons of water, so the salsa has a spoonable consistency. Season with salt, plus a little sugar, if you want to soften the tangy edge.