In a cocktail shaker, add 1.5 oz aged rum, 0.5 oz white rum, 0.5 oz orange curaçao, 0.5 oz orgeat syrup, 0.75 oz fresh lime juice, 0.25 oz simple syrup, and 1 dash Angostura bitters.

Add ice and shake

Fill the shaker with ice and shake vigorously for 10–12 seconds until well chilled (the exterior of the shaker should feel cold and slightly frosty).

Assemble

Discard the ice from the chilled glass if you chilled it separately. Fill the glass about three-quarters full with fresh crushed ice. Strain the shaken mixture over the crushed ice into the glass.

Float dark rum

Slowly pour 0.25 oz dark rum over the back of a bar spoon so it floats on top of the drink, creating the signature dark rum float.

Garnish and finish

Gently slap the mint sprig between your hands (to release aromas) and add it as a garnish along with a lime wheel or wedge. Optionally add a straw. Serve immediately.