Step 1

Muddle: Add the mint, lime, blackberries, and cane sugar to a flat-bottomed glass. Muddle for 10-15 seconds, until the sugar has dissolved and the mixture is juicy.

Step 2

Assemble the Cocktail: Pour the rum over the berry mixture, then top off with ice and club soda. Stir well, pulling the stir spoon slightly upward to evenly disperse the berries. Adjust the sparkling water, and sugar to taste as necessary and serve.