Add vodka cover jar and let infuse at least 1 hour and up to 8 hours.When ready to serve place 2 halves passion fruit into a cocktail shaker. Muddle until pulpy. Strain the basil infused vodka into the cocktail shaker, discard basil.
Add cointreau and cracked ice. Shake vigorously. Strain into 2 ice filled Collins glasses, dividing liquid evenly between them both. Top with club soda.