Step 1

Combine pisco, lime, simple syrup, and egg white in a cocktail shaker without ice and seal. Shake vigorously until egg white is foamy, about 10 seconds. Add ice to shaker and shake again very hard until well-chilled, about 10 seconds. Strain into chilled cocktail glass; dash bitters atop the egg-white foam.

Step 2

For simple syrup: In a jar, combine 1 cup water with 1 cup superfine sugar. Seal jar and shake until sugar is completely dissolved. Keep remainder refrigerated.