Combine 1/2 teaspoon of cocoa powder and 4 tablespoons of coarse sugar in a small bowl, then stir to combine. To rim the glass: - Spread the cocoa sugar on a small plate and dip the rim of the glass in a shallow pool of simple syrup. - Allow excess to drip off, then dip into cocoa sugar. - Set aside until ready to use for your chocolate martini recipe.