Ed - not sure what sauce they used - but here are some to try:
Soy sauce, 2T. rice wine vinegar, 1/2 tsp sesame oil & 1 tsp. minced scallion.
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1 tablespoon chili oil, 1 teaspoon distilled white vinegar, 1 tablespoon soy sauce
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2 tablespoons light soy sauce, 1 tablespoon rice vinegar, 1 teaspoon fresh ginger, minced
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Reduce a mixture of brown sugar, soy sauce and minced garlic until it is thick enough for dipping.
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1/4 cup tamari, 1/4 cup rice vinegar, 1/2 teaspoon freshly grated ginger, 1/2 teaspoon toasted sesame oil, 3 slices green onions