I used Goslings Black Seal & Monin Cinnamon for this. Needed a good 45 second stir, plus some additional dilution as it was fairly rich/sweet at first. Overall, the flavor is very unique. As G.M. Genovese mentioned, there's almost a cigar-like note in the mix, probably from the earthiness of the Cynar and smoke from the rum and cinnamon syrup. I liked this, but I also feel like I want to play around with it to try to reduce or balance the sweetness a bit more somehow...
El Dorado 8 turned out to be a good choice for this... The drink settles in after the first sip or two and the rum lends a toasty top note... Bit of a spicy cigar tone to this? Hmm.. a tasty, savory slup.