To make cranberry sprig garnish, carefully thread 3 fresh cranberries onto the bottom of each rosemary stem.
Fill a cocktail shaker with ice and add vodka, cranberry juice, and lime juice. Shake well and pour into ice-filled copper mugs. Top off mug with ginger beer and stir to combine.
Garnish with rosemary sprigs and lime wedges, if desired. Serve immediately.