The Tonka Bean
The bean of this South American legume tree has a distinctive vanilla flavor with some spicy cinnamon, clove, and almond undertones. It’s used frequently in perfumes, soaps, potpourri, and incense; and was for years a component of pipe tobacco. Because of its spicy-nutty nature, tonka is sometimes used as a substitute for mahlab or bitter almond.
But tonka beans are rarely seen as a vanilla substitute because it contains high levels of coumarin, a lethal anti-coagulant, also found in woodruff. You can reduce the amount of this compound by soaking the bean in alcohol and then allowing fermentation.
The beans are produced in Venezuela and Nigeria, but the Food and Drug Administration (FDA) has banned them for use as a food product in the United States. If you’re daring, they can be found through internet auctions for use in witchcraft and perfumery.