Dry shake the drink ingredients. This lets the protein in the egg begin to form foam instead of being diluted by the ice.
Then add ice and shake again. This cools the drink and strengthens the foam. Strain it into the glass, and you'll get a thick, white frothy layer.
Serve and garnish with mint if desired.
Recipe Note
There are many variations of this drink, but they all have a few basic ingredients: gin, lemon juice, sugar syrup, maple syrup, and club soda or soda water.