Candlenut: what it does, and what to use instead
Half fat, almost no flavour, and the ingredient most often dropped from recipes written for cooks abroad.
Buah keras means hard nut, and it is an accurate name. Candlenut is not a nut you eat. It is waxy, bland, faintly bitter, and its job in a rempah is structural rather than aromatic: it thickens, it carries fat, and it gives a curry body that it otherwise would not have.
It is also the ingredient most often quietly dropped from recipes written for cooks abroad, on the grounds that it is hard to find. What gets lost is not flavour so much as texture, and the loss is more noticeable than the substitution usually suggests.
What it actually does
Candlenut is roughly half fat. Ground into a rempah it behaves like a thickener and an emulsifier at once: it helps hold the oil and water phases together, and it gives the finished gravy a slightly velvety weight.
A curry made without it is thinner and separates more readily. You can compensate with more coconut milk, but that changes the balance, and a gravy thickened with santan alone tastes of coconut in a way that a candlenut-thickened one does not.
This is why it turns up in rendang, in most Malay curries, in laksa pastes and in gulai, and why it is invisible on the plate. It is doing its work in the background.
Do not eat it raw
Raw candlenut is mildly toxic, and eating a few will give you a thoroughly unpleasant afternoon. It is a purgative at best.
This is not a reason to avoid the ingredient. Cooking deals with the problem, and candlenut is always cooked: it goes into a rempah that is then fried for twenty minutes, or it is toasted first. Just do not snack on them while you are prepping.
Buying
Sold loose at wet markets and in packets at any supermarket, usually shelled, cream-coloured and roughly the size of a large marble.
You want nuts that still feel waxy and slightly oily, pale and even in colour. Shrivelled, yellowing or chalky ones have been sitting around. The fat that makes candlenut useful also makes it go rancid, and rancid candlenut puts a stale, faintly paint-like note through a whole pot of curry that you will not be able to remove.
Smell them. Fresh candlenut smells of very little, which is what you want. Anything sharp, in the way old nuts smell, means leave it.
Storage
Not the pantry. The fat is the problem, and a warm Malaysian kitchen cupboard is the fastest route to rancidity.
Airtight in the fridge keeps them in good condition for months. The freezer keeps them almost indefinitely and they grind straight from frozen without thawing. Given that most households use a handful at a time and a packet holds far more than that, the freezer is the sensible default.
Using it
Most recipes drop the nuts into the blender raw with everything else, which works. A light toast in a dry pan first, a few minutes until they smell faintly nutty and take a little colour, gives a rounder result and is worth the effort when the rempah is the whole dish.
They are hard, so give them a head start in the blender before the wet ingredients go in, or crush them roughly first. A stubborn whole candlenut that survives blending turns up later as a gritty white fleck.
Quantities are small. Three to six nuts for a family-sized curry is typical, and more is not better: too much candlenut makes a gravy heavy and slightly pasty.
Substitutes, honestly ranked
Macadamia is the closest by some distance. Similar fat content, similar waxiness, similar lack of assertive flavour. Use the same number of nuts. The only objection is price, and outside Malaysia macadamia is often the cheaper of the two anyway.
Raw cashew is the common substitute and it is decent. Slightly sweeter and slightly less fatty, so use a few more than the recipe asks for. Raw, not roasted or salted.
Blanched almond works at a push and is the weakest of the three. It thickens adequately but brings a distinct almond flavour that sits oddly in a rendang.
What does not work is leaving it out and adding cornflour. That gives you thickness without fat, which is a different thing entirely, and the gravy will taste of exactly what it is.
A note on the name
The English name comes from the old practice of threading the oily kernels onto a rib and burning them for light. That is genuinely what they were used for across the region, and it tells you most of what you need to know about the fat content.
The same nut appears as kemiri in Indonesia, doing much the same job in much the same pastes. If you are cooking from an Indonesian recipe that calls for kemiri, this is the ingredient, and the two are interchangeable.