This one appeared in an Esquire column in 1939. I came across it David Wondrich's (who also writes for Esquire) book Killer Cocktails. It's not too far removed from a Daiquiri. However, the addition of creme de cacao takes it to some other, slightly mysterious place. Your standard Daiquiri now gets rounded out a bit, some sweetness where it was bracing, smooth and silky where it was crisp, and an added layer of chocolate that manages to fit it without taking the whole thing over.
This one also calls to mind the Floridita (light rum, sweet vermouth, lime, creme de cacao, grenadine), which is interesting and tasty in its own right. In that one though the presence of creme de cacao is more restrained. Here, in the Ace of Clubs, it's more than a bit player but not quite a stage hog. Plus, the Ace of Clubs uses Barbados rum and the drink is better for it. Notes of molasses and wood are clearly driving this thing along.
Ace of Clubs - from Killer Cocktails, David Wondrich
2 oz Golden Barbados Rum
1/2 oz White Creme de Cacao*
1/2 oz Lime Juice
1/2 tsp Rich Demerara Simple (2:1)
Shake, Strain, Up
*This drink, like most, really does benefit from a decent brand here. A bottle is likely to last for a long, long time. Marie Brizard makes a nice one. And while I haven't tasted it yet, from what I've read the Tempus Fugit stuff sounds incredible.