Start by rinsing the blackberries and mint leaves thoroughly. Slice the lime and squeeze out fresh juice for the best flavor. Measure all ingredients beforehand so you can assemble the drink easily. This step makes the process quicker and more organized.
In a glass or shaker, add blackberries, mint leaves, lime juice, and sugar. Use a muddler to gently crush them until the berries release their juices and the mint becomes fragrant. Be careful not to over-muddle the mint, as it can turn bitter.
Pour in the coconut milk and white rum into the muddled mixture. Stir or shake gently to combine everything evenly. The coconut milk will give the drink a creamy texture that balances the tartness of the berries.
Fill the glass with ice cubes to keep the drink chilled. Top it off with club soda or sparkling water for that refreshing fizz. Stir lightly to blend all the flavors without losing the bubbles.
Finish by adding a few fresh blackberries and a sprig of mint on top. You can also add a lime wedge for extra flair. Serve immediately and enjoy the refreshing, tropical taste.