Tonka Bean is, in fact, a seed.
Mainly sourced from South America, it originates from the Dipteryx Odorata tree and is sometimes known as Coumarouna or Sarrapia, amongst other names.
This tree grows along Amazonian rivers and is harvested in May when the almond-shaped fruits will fall to the ground before undergoing a year-long drying process.
The seeds are extracted by breaking the out shell and contain a component known as coumarin which is vital for modern day perfumery. They are dried and soaked in alcohol (sometimes rum) so that they start to a develop a glaze comprised of coumarin crystals.
Coumarin, comprises nearly half of tonka beans chemical structure and emits an distinctly almond-like scent. Coumarin is not exclusive to tonka bean; it's found in smaller quantities in Liatris plants, as well in cinnamon (0.45%).
Perfumer Paul Parquet introduced coumarin to modern market in 1882 with 'Fougère Royale'; a fragrance that is dubbed as the father of the new popular fern fragrance family. Guerlain's 'Jicky' followed in 1868, propelling Coumarin to popularity.
Tonka bean, known for its gourmand nature (perfumery jargon for a scent that smells 'edible') and has a scent that is largely characterised by notes of vanilla, tobacco and almond. It is often noted to also have hay or pistachio-like nuances.
In the culinary realm, it's grated like nutmeg, enhancing chocolate, coffee, cakes, and desserts and was historically used to flavour snuff and tobacco pipes as well offering practical insights for therapeutic applications.