Place the mint leaves in a cocktail shaker. Muddle 4 to 5 times to extract flavor. Add the lemon wedges and muddle again.
Add the whiskey and simple syrup and fill the shaker with ice. Shake until cold and strain into a glass. If desired, add a splash of soda water. Serve with crushed ice.
Notes
For a pitcher of 8 drinks: Mix up a pitcher of 2 cups bourbon, 1 cup fresh lemon juice, and 1 cup simple syrup. Stir in 3 handfuls ice. To keep the flavor mint forward, muddle a few leaves in each glass before straining in 4 ounces.