In a cocktail shaker, combine the vodka, lemon juice, lime juice (if using), simple syrup, bitters, and egg white.
Shake vigorously without ice for about 15 seconds to create a frothy texture with the egg white (dry shake). Add a handful of ice to the shaker and shake again for approximately 30 seconds.
Strain the cocktail into a glass, allowing the foam to settle on top. Garnish with a cocktail cherry and a lemon wedge.