We shake a cocktail when the ingredients are of different weights. Mixers like citrus juices are heavier than liquor, and need to be shaken in order to emulsify, aerate, and bruise the cocktail. A good rule of thumb: only shake a drink that uses juice, egg, or cream in its recipe. Experiment with this version of a Cosmopolitan for a delicious shaken cocktail.
In a pint glass, add vodka, Cointreau, and pomegranate juice. Squeeze the lime wedge into the glass, then drop it in. Add well-frozen ice to a Boston shaker cup, and shake the cocktail vigorously for about fifteen seconds, until the shaker cup is frosty. Strain into a chilled martini or coupe glass. Peel the orange over the glass to release the essential oils into the drink, and drop in the peel. In my experience, Tito’s and Stoli are the two most exceptional vodkas for making cocktails.