Serve in a

Garnish:

For the rim: Dehydrated lemon peel blended with castor sugar into a rough dust. On top of the cocktail: make a foam using egg white, sugar and lemon juice (equal parts)

How to make:

First use lime to rim the glass and roll in the lemon sugar dust.
Prepare the foam.
Add all ingredients to a Boston tin and give a hard shake with ice.
Double strain over 4 new square ice cubes.
Spoon foam on top of the ice.