Combine all of the ingredients in a saucepan over high heat and bring to a boil, whisking gently. Reduce the heat and simmer, stirring occasionally, until the sauce is thick enough to coat the back of a spoon, for about 12 minutes. Remove from the heat. Serve immediately or store, refrigerated, in an airtight container overnight. Reheat in a saucepan over low heat.
Yield: about 2 cups