In a cocktail shaker (without ice) first combine the whiskey, espresso, averna amaro and simple syrup together. Then add the egg white and shake again until emulsified. Finally, add the ice and shake until chilled.
Double strain into a coupe glass and add a pinch of espresso powder to the top of the cocktail. Garnish with cocoa powder or a little bitters (optioal)
Notes
You can sub the simple syrup for a granulated low carb sweetener. Just be aware it may have a slightly grittier texture.