Cassareep is a thick black liquid made from cassava root, often with additional spices, which is used as a base for many sauces and especially in Guyanese pepperpot. Besides use as a flavoring and browning agent, it also acts as a preservative. Its antiseptic characteristics have led to medical application as an ointment, most notably in the treatment of certain eye diseases.
Cassareep is made from the juice of the bitter cassava root, which is poisonous (it contains large amounts of hydrogen cyanide, traditionally called "prussic acid" and blamed for many deaths) if it is not cooked properly. The acid is volatile and quickly dissipates when heated. Amerindians from Guyana reportedly made an antidote by steeping chili peppers in rum.
To make cassareep, the juice is boiled until it is reduced by half in volume, to the consistency of molasses and flavored with spices—including cloves, cinnamon, salt, sugar, and cayenne pepper. Traditionally, cassareep was boiled in a soft pot, the actual "pepper pot", which would absorb the flavors and also impart them (even if dry) to foods such as rice and chicken cooked in it.