Black soy sauce and kecap manis are both sweet soy sauces. By sweet, I really mean it - it's thick and viscous and basically a syrup.

Black soy sauce is a little saltier than kecap manis, but it shouldn't make too much of a difference when cooking. Just make sure you don't get Chinese black soy sauce, which isn't sweet at all. You'll know the difference because the Chinese stuff will be thin, while the sweet stuff is always thick.

They're delicious on dumplings and a top-tier ingredient in Pad Kra Pow.

If you can't find either, substituting equal parts soy sauce and sugar certainly won't kill anyone.