Treacle is a classic British ingredient, a dark syrup made in the sugar-refining process. Legendary London barman Dick Bradsell invented this cocktail in its honor, bringing those rich molasses flavors to the cocktail glass.
Apple juice is a rare ingredient in good cocktails; it’s usually too watery and weak to make a balanced drink. Here, Bradsell floats it atop the drink, which offers a brilliant contrast between the juice and the string dark rum beneath it.
Add the rum, simple syrup, and bitters to a short glass. Add ice and stir until chilled. Float the apple juice on top of the drink.