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.
I whipped up a nice batch of black truffle butter and the bitch gobbled it up when I spit it in her mouth.
Truffle Butter is when you are having anal sex and you put your penis inside of the vagina again, and it creates a brown~ish~tanbuttery substance around the vagina.
When fucking a woman in the ass. You would pull out of her ass and put your penis in her pussy. Mixing the fecal matter and the vaginal/seman to make truffle butter.