Step 1: Combine all the ingredients, minus the ketchup, in a large, deep, heavy saucepan and bring to a simmer over medium heat. Cook, uncovered, until all the ingredients are dissolved, stirring steadily, 5 minutes. Stir in the ketchup and bring to a boil. (Cover your stirring hand with a grill glove as the ketchup has a tendency to spatter.)
Step 2: Reduce the heat slightly and gently simmer the sauce, uncovered, until dark, thick, and richly flavored, about 30 minutes, stirring often. Transfer the sauce to clean jars and let cool to room temperature. Refrigerate until serving. The sauce will keep for several weeks.
How to use: As you would any barbecue sauce, that is to say, brushed on pork, ribs, and chicken towards the end of cooking and spooned freely over your favorite barbecue at the table.