(Optional) If you want to use crushed ice, add ice to a Lewis bag and smash it up with a wooden mallet. You could also use an ice crusher appliance if you have one.
Cocktail
Fill your serving mug with ice.
Add in the vodka, cranberry juice, and lime juice.
Top off the drink with the ginger beer, and give it a gentle stir just to combine everything.
Add in your fresh cranberries.
Clap the rosemary between your hands before adding it as a garnish.
Add the lime slice to the rim of the mug, and serve.