The Nonya cooking ingredient Buah Keluak or Indonesian Black Nuts undeniably, ambrosia among Nonya dishes, but like the durian it is an acquired taste. To the uninitiated, buah keluak is a black nut from Indonesia about the size of a misshapen golf ball. The surface is ridged with a smooth nut 'mouth' across the flattest part. A slit is made in this mouth through which one scrapes out the contents which have been variously described as 'opium' and soft tar'. The taste is indescribable and has to be eaten to be believed. Good nuts, when cooked, should be richly black and oily.
To prepare Buah Keluak or Indonesian Black Nuts, wash and scrub throughly until the thin film of dried mud they come in is completely gone. This has to be a proper job if do not want reconstituted mud in your keluak gravy. Soak in a large pot of water over-night or for at least six hours. An even quicker method is to boil the keluak for 15 minutes, which, I'm told by friends, works just as well.