In a medium nonreactive saucepan, bring the vinegar to a boil over high heat and cook until reduced by half, about 10 minutes. Add the soy sauce and cook until reduced by half again, 10 minutes longer. Remove from the heat, add the ginger, and let cool for 5 minutes.
Transfer the mixture to a blender, add the chili sauce, and blend until smooth. Transfer to a bowl and let cool to room temperature before using. The sauce will keep, tightly covered in the refrigerator, for up to 2 weeks.
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