Add the simple syrup (0.75 oz) and fresh lime juice (1 oz) to the glass with the mint. Using a muddler, gently press and twist 6–8 times — just enough to bruise the mint and release oils without shredding the leaves, which can make the drink bitter. If using raw sugar instead of simple syrup, add the 0.5 tsp sugar before muddling so it dissolves.

Add rum and ice

Pour the white rum (2 oz) into the glass. Fill the glass with crushed ice (about 1 cup), packing it lightly to the top.

Top and stir

Pour club soda (about 2 oz) over the ice to top the drink. Using a long bar spoon, stir gently 6–8 times from bottom to top to lift the mint and distribute flavors and carbonation evenly.

Garnish and finish

Give the mint sprig a light slap against the back of your hand to release its aroma, then place it and the lime wedge on top of the drink as garnish. If desired, add 1 dash of Angostura bitters on the foam for aroma and complexity.

Serve immediately with a straw positioned to sip through the mint and enjoy.