- 1 1/2 cups balsamic vinegar
- 3/4 cup hoisin sauce
- 2 tablespoons unsalted butter
- Simmer vinegar, hoisin sauce, and 1/2 teaspoon salt in a small heavy saucepan, uncovered, stirring frequently, until reduced to about 1 1/2 cups, 20 to 25 minutes.
- Remove from heat and stir in butter until melted.