Prep your glass: Use a rocks glass or a sturdy short tumbler. Fill it with crushed ice and set it aside to chill.
Muddle the base: In a cocktail shaker, add the peach slices, mint leaves, and ginger.
Pour in the simple syrup. Use a muddler to press and twist gently until the peaches are juicy and the mint is fragrant. You want to bruise the mint, not shred it.
Add citrus and bourbon: Pour in the lemon juice and bourbon.
Fill the shaker with ice.
Shake it: Shake vigorously for about 12–15 seconds, until the shaker feels chilled and frosty.
Strain and serve: Dump the ice from your glass. Add fresh crushed ice. Strain the cocktail over the ice.
For a smoother drink, use a fine-mesh strainer to catch mint bits and peach pulp.
Finish with fizz (optional): Add a small splash of sparkling water if you like a lighter, spritzier finish.
Garnish: Tuck in a mint sprig and a fresh peach slice. Give the mint a gentle slap between your palms first to release its aroma.