This Indonesian-style peanut sauce is much loved by the Dutch in their "adopted" (!) Indonesian taste. It goes really well as a basis for gado gado, and also with many other indonesian dishes. Having never been to Indonesia, I can only claim this is a good match to the sauce we get in the Netherlands!
NOTE: If you have "kecap manis", then use it! -- you can replace half the soy sauce with kecap manis, and reduce the sugar (leaving out perhaps a third of it). That gives a more authentic full flavour. It's not very common in Britain.
100ml (approx!) tamarind juice --- OR 25 ml (approx) tamarind paste
1 clove garlic
If using tamarind "block", remember to prep it first (by soaking the right amount in warm water for a few minutes at least).
In a small blender whizz up everything except for the garlic and the water. You can add a bit of the water, to make it easier to get it out again.
Crush the garlic and fry it in a little veg oil, in a milk pan or similar, just until softened (don't let it burn), Then add the blended mixture and cook it for ten minutes or more, stirring. Add water as it cooks, enough to get the consistency right.