Kecap manis, the sweetened Indonesian soy sauce, may be substituted with equal parts of Japanese or Chinese soy sauce and either dark brown sugar or molasses. The mixture is then simmered until the sugar dissolves.
Where kecap manis is hard to find, another commercially prepared substitute is Maggi's seasoning sauce, though it is not as sweet. Kecap manis can usually be found in an Asian specialty grocery store. The name on the label may be variously spelled "ketjap manis" and "kejap manis". It is pronounced kuh-CHOP MAH-nees, and is said to be the forerunner of Indonesian ketchup. In addition to sweetening and soy sauce, a good kecap manis will also be flavored with garlic, star anise and galangal.