From the 1930s, and the signature cocktail of the Ace of Clubs Lounge in Bermuda (known for its "luncheons, cocktails and dinners") this is a classic drink that has changed a lot over the years. The original cocktail called for a ton of white creme de cacao, but this recipe backs it off considerably and I swapped in the dark variety.
2 oz aged rum
1/2 oz lime juice
1/4 oz creme de cacao (Tempus Fugit)
couple of drops of Angostura or Abbott's bitters
Combine ingredients except bitters into a cocktail shaker, add ice, shake and double strain into a coupe glass. Add bitters.