Use only the original Indonesian sweet soy sauce or known as Kecap Manis. This sauce is thick, sweet and contains almost no salt. It is often used in the Indonesian kitchen, in particular for Satays. You can find it eventually in Asian shops. Though in western supermarket many varieties of "claimed to be indonesian sweet soy sauce" are available but personally I would say, those people have no idea of what kecap manis is" ;-((. Mostly those products taste really salty, worst than our salty soy sauce. These kind of product which give a bad name to people who use it in their first indonesian recipe.

However experience taught me a lesson and I have found a simple trick to recognize it's originality: 1. They usually label it completely "Kecap Manis or Ketjap instead of Indonesian sweet soy sauce only". 2. Just shake the bottle downside, if the sauce has a thick, almost syrupy consistency then you get it right. If it flows like water then never think a twice to even try, coz I have enough experience with them, especially in my first year living abroad and was desperately looking for my "beloved Kecap Manis" ;-)