Grate or chop the chocolate and place in a small shallow bowl or rimmed plate. Melt on low heat in the microwave. Dip the rim of the cocktail glass in the chocolate, and chill to set.
Combine the vodka, Chartreuse, crème de cacao and cream in a cocktail shaker with ice and shake well.
Strain into the chocolate-rimmed glass.
Grate additional chocolate curls over the top of the drink.
Top with a Cadbury Creme Mini Egg, cut open to reveal the "yolk."