Chocolate's history began in Mesoamerica, predating the Aztec Empire by at least 2,000 years. In today's food parlance, "Aztec Chocolate" has come to mean dark chocolate with a strong peppery flavor. It is marketed via ice cream, candy bars, hot chocolate mixes, etc. As such, it really isn't surprising that Fee Brothers sells an Aztec Chocolate bitters.
As I have found with all of the bitters I've explored in this series, the aroma hits you first and hits you hard. But how best to taste it on its own? Normally, I start with a gin and bitters but gin and chocolate didn't sound like a winning combo so I went with vodka instead.
The flavor is strong, too - indeed reminiscent of an Aztec hot chocolate. Many of the recipes I found online combine the bitters with tequila or mezcal, completing the Mexican theme. That might be worth trying, as might a hot cocoa concoction.