Pour each shot of espresso into a mug. To each mug, add 1/4 cup of the heavy cream and 1/4 cup of the chocolate liqueur. Top each mug with a dollop of whipped cream and a sprinkling of cocoa powder.
Using an electric mixer, whip the cream in a large bowl until soft peaks form. Add the vanilla and the sugar and continue to beat until it reaches the consistency of whipped cream.