This mild-flavored green salsa may be served heated or at room temperature. For the brightest green color possible, add the cilantro just before serving.

Preheat broiler. Arrange chiles on rack of a broiler pan and broil about 2 inches from heat, turning them frequently, until skins are blistered and charred, 8 to 12 minutes. (Alternatively, if using a gas stove, lay chiles on their sides on racks of burners and turn flames on high. Char chiles, turning them with tongs, until skins are blackened, 3 to 6 minutes.) Transfer chiles to a bowl and let stand, covered, until cool enough to handle. Wearing rubber gloves peel chiles. Cut off tops and discard seeds and ribs.
Remove husks from fresh tomatillos and rinse tomatillos under warm water to remove stickiness. In a saucepan, simmer tomatillos, broth, and garlic until tomatillos are tender, about 10 minutes if using fresh tomatillos and about 5 minutes if using canned. Add chiles to tomatillo mixture. Cool salsa slightly and in a blender pulse until coarsely chopped (use caution when blending hot liquids). Salsa may be made up to this point 2 days ahead and cooled, uncovered, before being chilled, covered. Bring salsa to room temperature or reheat before proceeding.

Just before serving, in a blender pulse salsa with cilantro until cilantro is finely chopped. Season with salt.