Start by making a strawberry basil syrup: Muddle strawberries with sugar to break berries down until sugar is saturated with juice. Add water and basil and allow the mixture to steep for 20 minutes. Stir and double strain until so that the juice is free of seeds. (The syrup can be refrigerated for up to 1 week.)

For the cocktail, place 2 oz. of the cold strawberry basil syrup into a cocktail coupe glass. Add Champagne or sparkling wine to fill and garnish with a basil leaf.