Which ingredient in a B-52 gives it its coffee flavor?

The ingredient that gives the B-52 its distinctive coffee flavor is Kahlua. Kahlua is a coffee liqueur made from a blend of coffee, sugar, vanilla, and rum. Its rich, dark flavor profile is essential to the B-52, which is typically layered with Kahlua at the bottom, followed by Baileys Irish Cream in the middle, and topped with Grand Marnier.

While Baileys provides a creamy texture and a subtle hint of chocolate, and Grand Marnier adds a citrusy orange flavor, it is Kahlua that imparts the bold coffee taste that is characteristic of the B-52 cocktail. Cognac, although a fine spirit, does not contribute to the coffee flavor and is not used in this particular cocktail. Thus, Kahlua is central to achieving the intended flavor balance in a B-52.