Balsamic vinegar might seem like an unusual ingredient in Mexican food, but it is common in Baja. This recipe makes more salsa than you'll need to make Shrimp with Spicy Chipotle Tomato Sauce, but it keeps in the refrigerator for weeks and can add an intense, smoky heat to grilled meats, stews and tacos. More Salsa Recipes
In a blender, combine the chipotle chiles with the molasses, balsamic vinegar, dark brown sugar and 1/4 cup of the water. Blend until the mixture is smooth.
Strain the sweet chipotle puree through a fine strainer into a small saucepan, pressing on the solids with a spatula to extract as much of the puree as possible.
Simmer the chipotle sauce over moderately low heat, stirring frequently with a heatproof rubber spatula, until it is very thick, pasty and reduced to 3/4 cup, about 20 minutes. Remove the salsa from the heat. Stir in the soy sauce and remaining 1/4 cup of water. Serve the salsa negra hot or at room temperature.