Combine the brandy, whole egg, simple syrup, and cream in a shaker without ice.
Dry shake vigorously for 15 seconds to fully emulsify the egg.
Add ice cubes and shake again hard for 10 seconds until well chilled.
Double-strain into a chilled whiskey sour glass.
Grate fresh nutmeg generously over the top to garnish.
The flip is one of the oldest cocktail categories, predating even the sling - originally served hot in Colonial-era taverns before the cold version became standard. Always dry shake first before adding ice: the initial shake without ice generates more friction and heat, which is key to fully emulsifying the egg into a seamless, custard-like texture.
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