Start by making the mint simple syrup. Add the sugar and mint leaves to a small saucepan. Using the back of a spoon, gently press the mint into the sugar to help release the oils from the leaves.

Add the water and warm everything over low heat, stirring until the sugar has completely dissolved. Remove the syrup from the heat and let it cool.

While the syrup cools, combine the blueberries, lime juice, and a little sugar in a small bowl. Gently mash the blueberries with a fork or muddler until they begin to release their juices.

To assemble the drinks, spoon some of the blueberry mixture into each glass. Add a splash of the cooled mint simple syrup, then fill the glass with ice. Top with sparkling water and stir gently to combine.

Finish with fresh blueberries, lime slices, and a sprig of mint before serving.