Begin by making the blueberry simple syrup. Combine the blueberries, agave, and water in a small sauce pan over medium heat. Stir and simmer until the mixture is heated and the blueberries are broken down. Muddle and smash the berries, pour through a mesh strainer, then set aside to cool.

Next, in a martini shaker, muddle together the rum, mint, lime juice, and lime quarters.

Fill the martini glass with ice and shake until chilled.

Pour the mixture through a strainer and divide it equally into two glasses.

To each glass add 1/4 cup of the blueberry syrup an top with lime soda.

Optional garnish: fresh blueberries and a sprig of mint