Put the port wine in a medium-sized saucepan and bring to a boil over medium-high heat. Reduce the heat and simmer for about 25 minutes or until the wine is reduced to a syrup. Remove from the heat and allow the reduction to cool. Transfer to a covered container or squeeze bottle and refrigerate until needed.
Pour the cream into a large saucepan and bring to a boil over medium-high heat. As soon as the cream boils, remove from the heat.
Add the blue cheese and using a handheld immersion blender, puree until smooth. Alternatively, transfer the cream and cheese to a food processor and process until smooth. Strain through a chinois or fine-mesh sieve into a large bowl. Season, to taste, with salt and pepper and set aside to cool at room temperature.
Pour the blue cheese mixture into the chilled canister of a foamer. The amount will fill it halfway. Charge it with 1 or 2 charges. Chill for at least 2 hours before serving.
To serve, shake the foamer vigorously and place a little blue cheese foam on a small plate. Garnish with a drizzle of port wine reduction. If it's too thick to drizzle, let the reduction come to room temperature. Repeat to make 5 to 7 more servings.
Recipe courtesy of Rick Tramonto, "Amuse-Bouche: Little Bites That Delight Before the Meal Begins", Random House, October 2002