Prepare your simple syrup by combining equal parts granulated sugar and water in a small saucepan. Heat gently, stirring until the sugar is completely dissolved. Let it cool before use. Store any extra in an airtight container in the refrigerator.

In a cocktail shaker, combine the Pisco, fresh lime juice, simple syrup, and egg white. Do not add ice yet. This is a 'dry shake' – seal the shaker and shake vigorously for about 15-20 seconds. This helps to emulsify the egg white and create a rich foam.

Add a generous amount of ice cubes to the cocktail shaker. Seal it tightly and shake again, this time for about 20-30 seconds, until the shaker is well-chilled. This is your 'wet shake'.

Using a fine-mesh strainer, double strain the mixture into a chilled coupe or cocktail glass. This ensures a smooth, frothy texture without any ice shards.

Garnish the top of the Pisco Sour with 2-3 dashes of Angostura bitters. You can use a toothpick to create a simple pattern if desired, but the traditional method is to simply dash them on.

Serve immediately and enjoy the delightful taste of Peru!