I first heard about tonka beans while watching the Great British Baking Show. One of the contestents used them to flavor a steamed pudding. I immediately had to google it and see what the heck tonka beans were and of course, order some to find out what they taste like!
Tonka beans are seeds found in a pulpy fruit of the Cumaru tree which primarily grows in northeastern South America. They are valued for their strong scent and interesting flavor and have been used in perfumes, as vanilla replacers, in cocktails and in pipe tobacco.
The most surprising thing I have learned about these beans is that they are banned in the US. You can buy them right off Amazon and nowhere does it tell you that they are illegal!!! I only learned this fact when I started researching them.
So, why are they banned? They contain a small amount of a compound called coumarin, which is toxic in large doses. Apparently, you’d have to eat about 30 whole beans, roughly 250 servings, to harm you. There has been some efforts to change this law, but so far, it is still in effect. Nutmeg has similar properties, just over a teaspoon of nutmeg can cause severe health problems ranging from hallucinations to organ failure. Other spices have similar issues, but are considered safe because we only consume small quantities. It is unclear to me why tonka beans get the ban, but other spices or potentially toxic foods don’t.
Regardless, I still wanted to see what they taste like, so I ground them up to a powder and added them to two foods: a vegan pudding and dark chocolate. The aroma of the beans is very strong, possibly stronger than the flavor. I’d describe it as clove, vanilla, pipe smoke, spicy, bitter almond/amaretto or cherry (benzaldehyde). I found the flavor to be more subtle. I may have used too much, but the pudding had some odd bitter notes. The combination with dark chocolate was more appealing. It gave the chocolate an interesting aroma and some vanilla, clove, licorice type notes.
Tonka bean in the fruit (not my picture) 
Tonka Beans out of the package with a pencil for size reference. 
Dark Chocolate flavored with Tonka, powdered form and beans. 
Tonka Bean flavored pudding
It is amazing to me how many foods are out there that are unknown to me. This is one appreciation I have for technology and global supply. We can learn so much so quickly and get access to things we may have never heard of in the past.
EAT Food Consulting 