On an ungreased skillet or griddle set over medium heat, roast the chiles and garlic, turning everything regularly, until they are soft and darkened in spots—most everything should be done in about 15 minutes. Let them cool to room temperature, then slip off the skins from the garlic. Scoop the chiles and garlic into a blender jar along with ¼ cup water, the lime juice and ½ teaspoon salt. Blend until it is a smooth puree and pour into a small dish. Stir in a little water if need to give the salsa a consistency that is easy to spoon on in drops. Taste it cautiously (a drop will usually be enough). Add more salt if necessary to balance the heat and acid. Pour into a serving dish and put out for your guests to use as they like.