Prepare the Blueberry Syrup: In a medium saucepan, combine the blueberries and 1 cup of water. Bring the mixture to a boil over medium-high heat. Reduce the heat and let it simmer for about 10 minutes, until the blueberries are soft and release their juices. Use a potato masher or the back of a spoon to gently mash the blueberries and release more juice. Remove from heat and let it cool slightly.
Strain the Syrup: Strain the blueberry mixture through a fine-mesh sieve into a bowl or a large measuring cup, pressing on the solids to extract as much liquid as possible. Discard the solids and set the strained syrup aside to cool completely.
Make the Lemonade: In a large pitcher, combine the freshly squeezed lemon juice and sugar. Stir until the sugar is completely dissolved. Add the cooled blueberry syrup to the pitcher. Add the remaining 3 cups of water and stir well.
Serve: Fill glasses with ice cubes. Pour the blueberry lemonade over the ice. Garnish with lemon slices and fresh mint leaves if desired.
Enjoy: Serve immediately and enjoy this refreshing summer drink!
