Put the (unpeeled) garlic in a heavy skillet over low heat and cook, turning occasionally, until it browns on a couple of sides, about 10 minutes. Remove and squeeze the garlic from its skins directly into a blender.
Meanwhile, soak the chiles in boiling water until soft, about 5 minutes. Remove (carefully; they’re hot) and peel the flesh away from the seeds and stems. Put the flesh in the blender with all the remaining ingredients.
Add (fresh) boiling water to about the 2 cup mark and blend until smooth. Taste and add more salt (or anything else you like) to taste. This keeps well in the refrigerator.