Didn't have Zacapa 23 on hand so substituted Zaya Grand Riserva 12yr instead. Unique cocktail but may be a little too rich for my taste. I'll try it with Barbancourt 15yr and up it to 1 1/4, minus the simple syrup and see how that works.
no exotic rum on hand, had to make do with Bacardi 8 años...actually went a little heavy on the rum, could do with a bit less lime. Like the combination of Green Chartreuse and Thai Basil, lots of interesting herbal notes (and the anise-like notes of both complemented each other). Used a ginger simple syrup I'd made, nice addition. Also, garnishing with a basil leaf (actually, a small stalk with a pair of leaves) is a nice touch.