Place sugar and water in small saucepan over medium heat. Stir until sugar is fully dissolved. Refrigerate any leftover simple syrup in an air-tight container for up to 1 month.

In a small bowl, add the sugar and lemon zest; stir until well combined.

To prepare the rocks glasses, place the lemon sugar on a plate. Wet the rim of the glass with a bit of water and then invert the glass into the lemon sugar. Twist the glass a couple of times and then turn upright; repeat with remaining glasses. Set glasses aside.

In a cocktail shaker, add the mint leaves, lemons, blueberries and simple syrup; muddle well.

Add bourbon and ice; shake well.

Fill prepared rocks glasses with crushed ice. Strain bourbon smash into the prepared glasses.

Garnish with additional mint spring, lemon wheel or fresh blueberries.