I use rye for this because I don't love bourbon. Something boozy like Rittenhouse really cuts through the mint and the sugar to still taste like a real drink.
||big spearmint leaves
Blender muddle the mint leaves in the bourbon (or, use a muddler on the mint leaves in the whisky). Pour into julep cup, add simple syrup and some crushed ice. Stir until the glass frosts. Top with more ice. Smack a mint sprig between your hands to release the aroma then garnish with mint and a straw.