Muddle 5 blueberries with 3/4 ounce ruby port in a small bowl; strain into a flute. Slowly top with 4 ounces cold prosecco or other dry sparkling wine. Garnish with a few whole blueberries.
To make a proper cocktail, shake or stir with ice for 20 to 30 seconds — it’s longer than you think! This will dilute the drink just the right amount and make it extra cold.