When whisking well-chilled whipping cream with a butterfat content of 30 to 35 percent at medium speed, its volume increases. Lightly whipped, foamy whisked cream contains the most possible air, and this is the stage at which it is ideal to make a chocolate mousse, for example. The volume has increased by 220 percent. If we continue to whip, not only will we no longer imprison any air, but the volume will diminish. The cream is transformed into Chantilly cream, which is to say that its volume is now only 160 percent of the original. If we continue to whisk, it will change into butter!