Clap the basil leaves between the palms of your hands and add to a cocktail shaker. Add Evan Williams Peach, lemon juice, agave and ice and shake until chilled.
Add 4 blackberries to a cocktail glass and muddle. Fill the glass with ice. Strain the cocktail mixture into the glass. Top with prosecco.
If desired, garnish with a peach slice and edible flower.