To make the simple syrup, combine water and sugar in a medium saucepan. Bring the mixture to a boil and stir until the sugar dissolves. Let the mixture cool.

Pour ⅓ cup of the simple syrup into the bowl of a blender. Add blueberries and puree until smooth.

Place a fine-mesh strainer over a medium bowl and pour the blueberry mixture into the strainer. Using a rubber spatula, gently press the blueberry mixture through the strainer. Discard the seeds left in the strainer.

Spoon 2 to 3 tablespoons of the blueberry puree into each of 6 champagne flutes. Add 4 to 5 fresh, whole blueberries to each glass. Fill the glasses with chilled Prosecco (or another sparkling wine). Gently stir and serve.