Created by Simon Difford in 2017 at the Cabinet Room, London, England. Despite the name, it is a dry spiritous cocktail; the "sweet" refers to the use of sweet vermouth.
Half-fill a mixing jug with ice.
Add all ingredients and stir until well-chilled.
Strain into a chilled cocktail coupe.
Balance a square of 80% cacao chocolate on the rim as garnish.