Combine gin, lemon juice, lime juice, simple syrup, heavy cream, egg white, orange blossom water, and vanilla extract in a cocktail shaker without ice.
Dry shake vigorously for 60 seconds to emulsify the cream and egg white.
Add ice and shake hard for a further 2 minutes until the shaker is very cold and the mixture is thick and frothy.
Double strain into a chilled highball glass.
Slowly top with chilled soda water, pouring gently down the side of the glass to lift the foam above the rim.
The extended dry shake before adding ice is essential - it builds the emulsification of cream and egg white that gives the Ramos Fizz its signature meringue-like foam. Henry Ramos reportedly had up to 35 shaker boys working in relay on busy nights just to keep up with orders.
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