Make a simple syrup. In a small saucepan, mix the sugar and water and bring to a boil. Once the sugar has dissolved, turn the heat off and cool down the simple syrup. This can be made ahead of time. Set aside 1.5 ounces of simple syrup.
Add the Pisco, passion fruit juice, lime juice, egg white, and 1.5 oz of simple syrup in a cocktail shaker. Cover the cocktail shaker and shake as hard as you can for 10 seconds.
Remove the lid, add the ice cubes, cover, and shake again for 10 more seconds.
Pour the Passion Fruit Pisco Sour through the cocktail shaker strainer and into a chilled glass. The liquid will pour first, followed by the egg white foam to create its distinct foamy layer.
Serve and enjoy.