Originally posted here:
Half cup each: sugar (white, or white and dark mixed), Kikkoman soy sauce.
Two tablespoons each: sherry, dark vinegar.
One teaspoon salt.
One whole star anise, one or two slices of ginger, and a clove or two.
Put everything except the vinegar and half of the soy sauce into a saucepan. Heat gently, stirring, till the sugar is fully dissolved and the liquid syrupy and starting to foam. Stir in the remaining soy sauce and in a minute or so turn off the heat. Let it cool and strain it into a bottle. Use the dark vinegar to swish the remaining syrup coating the inside of the saucepan, and add to the bottle.
This is as close to typical Dutch and Indonesian sweet soy sauce as you can get, and far better than most brands. And you know what is in it.