1/3 cup soy sauce
2 tbsp. mirin (sweet Japanese rice wine) or medium-dry sherry
2 1/2 tbsp. cider vinegar
2 tbsp. sugar
1 1/2 tbsp. chopped peeled fresh gingerroot
In a small saucepan simmer sauce ingredients, stirring until sugar is dissolved, until reduced to about 1/2 cup and cool to room temperature in a metal bowl set in a larger bowl of ice and cold water.