Add 30ml light rum, 30ml ruby port, 22ml fresh lemon juice, 5ml simple syrup, and one egg white to a shaker without ice.
Dry shake vigorously for 10–15 seconds to emulsify the egg white.
Add ice and shake again for 10–15 seconds until well chilled.
Double-strain into a highball glass over two large ice cubes.
Top slowly with 60ml chilled soda water and give one brief, gentle stir to integrate.
Serve immediately.
Use a fine-mesh strainer on top of your hawthorne strainer when double-straining to keep the foam tight and cloud-free - the egg white foam is the visual and textural heart of this drink. Powdered sugar was traditional in the original recipe but simple syrup integrates more cleanly without graininess.
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