Bring 1/3 cup water and 1/3 cup sugar to a boil over medium heat. Once the sugar is dissolved, dip 2 sage leaves carefully in the hot simple syrup, shaking off the excess. Roll the leaves in a light coat of sugar and lay flat on a plate to cool and harden in the refrigerator.
In a shaker, muddle together blackberries with 8 sage leaves. Pour in gin, lime juice and simple syrup and fill with ice.
Shake and strain evenly between into two glasses filled with ice.
Top with club soda and garnish with extra blackberries and candied sage leaves.