Put two small tumblers in the fridge to chill overnight. Put 30g of the chocolate in a shallow bowl and melt in the microwave in short bursts. Dip the rim of the chilled glasses in the melted chocolate, then stand them upright so it gradually drips down the sides. Return to the fridge until you're ready to serve.

Fill a cocktail shaker with ice, then pour in the coffee-flavoured liqueur, vodka, Irish cream liqueur and double cream. Shake until the outside of the shaker is very cold.

Put a few ice cubes in the prepared glasses, then strain in the cocktail. Finely grate over the remaining chocolate and serve with a paper straw.