Wipe the rim of a chilled, oversized martini glass with lemon wedge.
Pour sugar and chocolate into a saucer and mix well.
Dip glass rim in mixture and roll to thoroughly coat rim.
Over a large handful of ice in a cocktail shaker, pour espresso, vodka, and creme de cacao. Shake until frothy. Strain into prepared glass. Garnish rim with a twist and stand back.