Place the gin, POM Wonderful 100% Pomegranate Juice, lemon juice, simple syrup, and egg white in a cocktail shaker. Shake vigorously for 15 seconds.
Fill the shaker with ice and shake for 30 seconds until cold.
Strain the drink into a glass and top with the soda water; the egg white foam should form on top. If desired, garnish with a rosemary sprig. Serve immediately.
