If you want to decorate the glasses with grated chocolate, do it before making and adding the cocktail to the glass. To decorate the glass: dip the rim of the glass into soft ice cream, chocolate syrup, or melted chocolate and then into the grated chocolate. (To make grated chocolate, you can use a fine cheese grater to grate a chocolate bar.)
Combine ice cream, ice, Crème de menthe, Crème de cocoa, and vodka in a blender and blend until completely smooth.
Divide the mixture between two glasses and garnish with some whipped cream and grated chocolate.
Want to make it non-alcoholic? Use the same vanilla ice cream and in addition to ice cream, add about 1/2 cups of milk, 1 cup of ice, 2-3 tablespoons of crème de menthe syrup (non-alcoholic and can be found in coffee syrups isle and mixers isle of the grocery store), and either a couple of tablespoons of chocolate syrup or a couple of ounces of a chocolate bar. Blend it all and serve.