1.   Cook in lightly greased skillet on medium-low heat until bubbles form on top.

2.   Heat until a few bubbles form around the edge of the pan.

3.   Hot chocolate should be heated in a deep pan over medium heat just until bubbles form around the edge.

4.   In medium saucepan, heat cream until small bubbles form around edge of pan.

5.   Place over medium heat, and bring to a simmer, stirring constantly, just until bubbles form around edges of pan.

6.   The air bubbles form because of an effect called cavitation.