Combine the soy sauce, wine, sake or sherry, sugar and ginger in a small saucepan.
Bring to a boil and then simmer over medium heat 3 minutes.
Blend water with cornstarch; stir into sauce.
Stir over medium heat 1 minute or until thickened.
Makes about 1 cup.
Set aside to cool or refrigerate up to 1 week.
Use as marinade for chicken, beef, pork or seafood.