"According to the entry in the patent database, Aero bars are formed by a method involving chocolate in a liquid state on the verge of solidifying. Air is run through the chocolate with a vacuum as it cools (in the form of many very small bubbles), resulting in evenly distributed bubbles throughout the bar and a honeycomb-like texture.
The exact procedure for making the bubbles is a closely guarded secret. The question of how the bubbles are so evenly distributed throughout the chocolate was the subject of a question in one issue of New Scientist, which made it into the compendium of readers' questions Does Anything Eat Wasps?. A spokesperson for Nestl� provided some clues but there has been no definitive answer."