Gather 5 large mint leaves - or more if the leaves are smaller - and smack and pull up along the inside of the Julep tin. Discard that mint and add simple syrup and Bourbon to the tin.
Stir with a spoon and fill the tin halfway with crushed ice, then swizzle for a few seconds. Move quickly and fill the tin to the top and pack, creating the crushed ice snow cone.
Insert a Julep straw and put the mint sprig garnish next to the straw.