I found a review on Amazon--Ouch.
Aztec Chocolate Bitters--The Bitter Truth,
This review is from: Fee Brothers Aztec Chocolate Cocktail Bitters - 4 oz (Kitchen)
I'm sorry to say the Aztec bitters are a terrible product. I do enjoy some of the Fee Brother's other bitters, the orange and the whiskey barrel. But this one reeks of artificial chocolate flavoring and I didn't detect the slightest bit of heat or spice--just cloying sweetness all the way. If you're at all serious about cocktails, don't throw your money away. I think this was a flimsy attempt to compete with the new Bitterman's line that's coming out soon. If you happen to try the Fee Brother's chocolate bitters anyway, don't even think about experimenting with a Manhattan. Don't do it--your whiskey will never forgive you.