Mixologist Adam Seger believes that a great rim on a cocktail takes the integral flavor components of a drink (in this case, cocoa, coffee and sugar) and combines them with complementary flavors (like the allspice here).
MAKE THE COCKTAIL
Combine the sugar, allspice, coffee and cocoa powder in a bowl.
Moisten the outer rim of 4 chilled martini glasses with the orange; coat lightly with the mocha sugar. In a blender, combine all of the remaining ingredients and blend until smooth. Pour into the glasses.