Using a cocktail shaker with both the strainer and solid top, fill the cocktail shaker 2/3 full with ice. Add all of the ingredients except the chilled soda water. Secure the top onto the shaker and shake the shaker as hard as you can for thirty seconds. Change hands and shake again for thirty more seconds. If you’re using a pasteurized egg white, take a deep breath and shake again for thirty seconds (pasteurized egg whites take longer to foam up than unpasteurized).
Strain into a cocktail coupe (you may need to remove the shaker top and spoon the foam onto the top of the drink) and top with chilled soda water. Serve immediately.