What is argan oil — and what's the difference between culinary and cosmetic?

The argan tree grows almost nowhere on earth except a stretch of southwest Morocco between Essaouira, Agadir and Taroudant — gnarled, thorny trees that goats famously climb to reach the fruit. The first cooperative I visited near Essaouira had women sitting on the floor cracking the rock-hard nuts between two stones, one strike each, with a rhythm that never missed. Inside each nut are the kernels that become oil. It is brutally slow work, which is the first reason real argan oil is never cheap.

The crucial fork is roasting. For CULINARY argan oil, the kernels are gently roasted before pressing, and that toasting is everything — it gives the oil a deep amber colour and a rich, nutty, almost hazelnut-and-sesame aroma that fills the room when the lid comes off. I have watched first-timers dip warm bread into a saucer of it and go quiet. For COSMETIC argan oil, the kernels are left raw and cold-pressed, producing a paler, much lighter oil that is nearly odourless — because nobody wants their face cream to smell of roasted nuts.

Culinary argan belongs on the table, not in the frying pan — its flavour is too precious and its smoke point too low for cooking. We drizzle it over salads, swirl it into a bowl for dipping bread at breakfast, trickle it over couscous, and above all blend it into amlou: that addictive paste of argan oil, ground almonds and honey that Moroccans eat with bread and which tastes like a savoury, grown-up praline. A spoonful of amlou with mint tea is one of the great small pleasures of the south.

When buying, let your nose decide. Real culinary argan smells unmistakably toasted and nutty; cosmetic argan smells of almost nothing. Buy from a women's cooperative where you can watch the cracking and pressing — both for quality and because those cooperatives are a genuine source of income for Berber women in the region. Avoid roadside bottles with no provenance: argan is heavily faked, often cut with cheaper oils. The real thing, roasted and golden, is worth carrying home carefully.