Combine pisco, sugar, lemon juice, and egg white (if using) in a cocktail shaker.

Add crushed ice to the shaker.

Shake vigorously until well chilled.

Strain into a stemmed cocktail glass.

Garnish with a lime wedge or a few drops of bitters (optional).

For the Cachaca variation, wash a lime and roll it on a board.

Cut the lime into 8 pieces.

Place the lime pieces in a double rocks glass.

Sprinkle with sugar and muddle the limes.

Add the cachaca.

Stir to mix and dissolve the sugar.

Add ice and stir again.