One genesis for fatCoffee is the traditional Tibetan drink, po cha, or butter tea. (The other is Niter Kibbeh, a traditionally Ethiopian preparation of butter for use in butter coffee ceremonies and other gatherings.)
Typically, po cha is made with fermented yak butter and black tea. Unlike most western butters yak butter is more cheese-like in texture and taste, imparting a typically salty taste to the tea preparation. It can be something of an acquired taste, so omitting the salt in the recipe below is perfectly reasonable.