Bring about 3 quarts of water to a boil in a large pot or Dutch oven. Add the white wine, salt, peppercorns, parsley stems, if using, thyme, bay leaves, shallots and garlic. Bring back to a boil, and then reduce to a simmer and let the flavors meld, about 10 minutes. Add the shrimp and cook just until opaque and pink, about 2 minutes. Remove from the liquid and shock in an ice bath to stop the cooking. Serve chilled.