With its hypnotic aroma, often described as a combination of vanilla, cloves, almond, pear and even fresh hay, it’s little wonder this wrinkled little seed from a South American hardwood tree has been a favoured ingredient for perfumiers for many years.
But these same aromas also make it a popular ingredient in the kitchen. Tonka beans are most often used in sweet dishes to add a more complex and interesting vanilla flavour, and they are particularly popular in high-end Parisian patisseries, where they’re used to enhance the flavour of baked goods. The beans are also often boiled with cream or milk, and the resulting infusion can then be used to make ice-cream, chocolate and mascarpone desserts.
However, their slight bitter almond edge also works well in savoury dishes, such as mashed potato, sauces and soups. We’ve used them in place of vanilla to make the Réunion Island dish of poule à la vanille (tonka bean and rum-braised chicken).
In Italy, you might come across tonka beans in tartufi alla fava tonka (tonka bean truffles) or even panna cotta. In South America, the tonka bean is made into a paste and then mixed with milk to make a sweet drink, while in France, it is often found in crème brûlées, sabayons and even éclairs. It can also be used as a substitute for bitter almonds and mahleb (a spice used in Middle Eastern and Greek cooking, made from ground cherry kernels).
Once harvested, tonka beans are dried, then soaked in rum for up to 24 hours and dried again. Fermentation occurs, causing a thin veil of coumarin crystals to form, and this produces the characteristic flavour.
You can find tonka beans at selected spice shops and specialist food shops. To use, you simply need to grate the bean very finely (using a Microplane is best), but never use more than the stated amount in the recipe, as tonka beans contain coumarin, which is an anticoagulant and in high doses, it is considered toxic. However, the tonka bean is a strong spice (akin to nutmeg) so it only takes a very tiny amount of the bean to flavour a dish, which makes it safe to use.
Photography by John Laurie.