BLUEBERRY SIMPLE SYRUP: Add granulated sugar and 1 cup water to small saucepan, over medium heat. Heat and stir until the sugar is dissolved.
Add in fresh blueberries, boil for 5 minutes, until blueberries start to break down.
Pour mixture through a fine mesh sieve into a small bowl and set aside to cool to room temperature.
LEMONADE: Pour thawed lemonade concentrate and 2 cups cold water into a large pitcher. Slowly pour in chilled club soda. (Be careful, it will fizz up a lot.) Stir to combine, place in refrigerator until ready to serve.
SINGLE SERVING: Pour 2-3 tablespoons of blueberry simple syrup in the bottom of glass, top with ice, pour in lemonade. Garnish with fresh blueberries, lemon slices, and mint sprigs.
If serving a group, you may want to pour the blueberry syrup directly into the pitcher of lemonade, instead of individual glasses. This would also be very pretty in a punch bowl.