Truffle butter is created when you pull your dick out of the asshole and proceed to fuck her in the pussy, the fecal matter, vaginal juices and semen combine to form a tan buttery substance in and around her pussy;
truffle butter.
Black
truffle butter is created when the woman is menstruating.
The entomology of the term stems from the English black pudding or the French boudin noir, both made with blood.