4ouncesprosecco, or bubbly of your choice, chilled
To a cocktail shaker filled with ice, add bourbon, simple syrup, and vanilla extract; shake vigorously for 15 seconds.
Strain into a chilled champagne flute or tall narrow glass and top with prosecco.
Homemade vanilla simple syrup can be used in place of the simple syrup and vanilla extract. To make vanilla simple syrup, add 1 cup water, 1 cup granulated sugar, and 1 teaspoon vanilla extract (or 2 vanilla beans split down the center) to a small saucepan and bring to a light simmer for 10 minutes. Then allow the syrup to cool to room temperature before discarding the beans (if using) and using or bottling.
For a lighter cocktail, add 6 oz. of prosecco instead of 4 oz.