buah keluak — Central Java, Indonesia

Buah keluak is the fermented kernel of the Pangium edule tree, naturally toxic when raw and rendered safe through burial and fermentation over several weeks, after which the black, custard-like flesh inside the hard shell can be scooped out and cooked. Used in a stew, it turns the broth a deep brown-black and lends a smoky, faintly bitter, almost cocoa-like depth that no other ingredient quite replaces. It is reported from Central Java, where the prepared nuts are bought ready-fermented from markets — few households ferment their own — and cooked into a stew with chicken or beef as part of home cooking and small eateries. To prepare it, the shells are cracked open and the black flesh is scraped out, mixed with a little of the cooking liquid to loosen it, and blended into a paste with shallot, garlic, galangal, candlenut and chili that has been fried until fragrant. Chicken pieces go into the pot with this paste, water or stock, and simmer slowly until the meat is tender and the broth has taken on the nut's dark color. What distinguishes this stew from other Javanese chicken dishes is entirely the buah keluak itself — its bitterness has to be balanced carefully against salt, a little sugar and often tamarind, since too much nut turns the broth acrid while too little leaves the color without the flavor. Households vary how many nuts go into a batch and how long the chicken simmers, since the flesh keeps softening the sauce the longer it cooks.