Add 5ml simple syrup, 10ml water, 30ml fresh lemon juice, and 60ml bourbon to a cocktail shaker.
Fill the shaker halfway with ice cubes.
Shake vigorously for 10–12 seconds.
Strain into a highball glass over fresh ice.
Express a lemon peel over the surface, run it around the rim, then place it on the rim or drop it into the glass as garnish.
Expressing the lemon peel directly over the surface rather than simply dropping it in makes a meaningful difference - the spritz of citrus oils lifts the aroma and softens the spirit on the nose before the first sip.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including Bourbon Sling.