Add the blackberries, basil, honey, and water to a small saucepan set over medium heat. Simmer, stirring occasionally, until mixture is heated through and starts to thicken, approximately 4-5 minutes. Gently press on blackberries while heating to release juices.

Remove from heat and strain mixture through a fine mesh strainer to remove solids. Reserve remaining liquid and set aside to cool.

If using, divide the Elderflower liqueur among four champagne flutes, along with a drizzle of the blackberry simple syrup. Finish by topping off each glass with some chilled Prosecco.

Garnish each glass with 2-3 fresh blackberries and a sprig of fresh basil, if desired, before serving. Enjoy!