Add the lemon juice, simple syrup, gin, and egg white to a cocktail shaker that is about half full of ice. Shake really well!
Pour into glasses, but strain out the ice, and serve right away!
To make your own simple syrup add one part sugar to one part water to a pot on the stove and simmer till the mixture thickens slightly so that it coats the back a spoon. Cool before using and store in a small mason jar in the fridge.