Troubleshooting:

“My chocolate mousse is often grainy.”

Be careful to reheat your chocolate mixture slightly before you incorporate the whisked egg whites or whipped cream. If the mixture has already cooled and you add a large quantity of egg whites or cold cream, the chocolate hardens and forms grains.

“There’s liquid egg white at the bottom of my mixing bowl.”

Make sure that you whisk your egg whites until they form soft peaks, when they should bend over slightly. If they are whisked to the firm peak stage, mixing them with the chocolate will deflate them, and deflated egg whites liquefy.