Place shallot, onion, Vineyard Creek Pinot Grigio, butter, and vinegar in a large heavy pot. Add mussels, cover, and bring to a boil. Cook, gently shaking pot once or twice, until mussels open, 3-5 minutes (discard any mussels that don't open). Set a strainer lined with a double layer of cheesecloth over a bowl; set aside. Using a slotted spoon, transfer mussels to a large bowl. Pour mixture in pot through prepared strainer. Season broth with pepper and pour over mussels. Sprinkle with parsley.