Combine crushed ice, vodka, peach nectar, orange liqueur, and 1 white cranberry juice in a cocktail shaker. Squeeze juice from lemon wedges into shaker. Place wedges in shaker. Cover with lid, and shake vigorously until thoroughly chilled (about 30 seconds). Strain into a 6- to 8-oz. glass; discard lemon wedges and ice. Top with sparkling white wine. Garnish, if desired.