In a cocktail tin, shake egg white until foamy. Add next five ingredients and six cubes of ice. Shake tin until ice melts (and you can’t hear it shaking). Pour 2 ounces of soda into a chilled 12-ounce collins glass and strain liquid over top. Tap glass five or six times to settle, then top with remaining soda and grated hazelnut.
From Hot in the City.