Crumble the brownies or chocolate biscuits. Except for the ingredients intended for decoration and serving, fill everything into a cocktail shaker or mixer or blender and shake or process for 30 seconds.
Chop the ginger very finely. Pour the finished drink into a highball or shake glass filled with ice cubes and top with a layer of crushed ice. Garnish the drink with chocolate shavings and a touch of fresh ginger.