In a mixing glass, muddle mint leaves a few times with the pomegranate juice using a muddler or the back of a wood spoon. This helps to release the mint flavor. Add ice and stir. Add the club soda or sparkling water.
Divide the pomegranate mixture among 3-4 glasses and fill with ice cubes. Top with ginger beer till full and stir one more time. Garnish with fresh mint and pomegranate arils.
Freeze the pomegranate juice and mint or rosemary into ice cube molds to make ahead. Pour ginger ale on top (see picture in the post for how to do this). Rosemary looks better when frozen!
See post on edits to make for a crowd (10 people) or adjust the serving size in the recipe card accordingly.