Chill a double rocks or Tiki-style glass by filling it with ice and setting aside. In a cocktail shaker, add 2 oz aged rum, 0.75 oz fresh lime juice, 0.5 oz ginger liqueur, 0.5 oz falernum, 1 oz fresh pineapple juice, 0.5 oz cloudy apple juice (or cider), 0.5 oz demerara syrup, and 2 dashes Angostura bitters.

Shake

Fill the shaker with ice, cap it, and shake vigorously for 12–15 seconds until well chilled and slightly diluted.

Prepare glass

Dump the ice from the chilled glass and fill it with fresh crushed ice until slightly heaped.

Double-strain and pour

Double-strain the shaken cocktail over the crushed ice in the prepared glass to remove small ice shards and pulp for a clean texture.

Float dark rum

Carefully pour 0.5 oz dark rum over the back of a bar spoon to float it on top of the drink. This creates the 'red tiger' dark-top appearance and aroma contrast.

Final touch

Add 2 more dashes of Angostura bitters on the foam/ice if desired and gently press a mint sprig into the ice so leaves release aroma without wilting.

Garnish

Garnish with a lime wheel on the rim and a mint sprig tucked into the crushed ice. Lightly grate 1/4 tsp nutmeg over the top if using. Serve with a straw and a small cocktail pick for the lime.