Muddle your mint. Combine your mint, rum, lime juice, and sweetener in a cocktail shaker. Then use a cocktail muddler to gently muddle the mint a bit so that those fresh minty flavors get released.

Shake with ice. Add ice to the cocktail shaker, then cover and give it a good vigorous shake for about 15 seconds until chilled.

Strain then top with club soda. Strain the mixture into a tall glass filled with ice, being sure that an inch or so is left at the top of the glass. Top off with club soda.
And serve! Garnished with lots of extra fresh mint