This chocolate mousse recipe is so simple and so delicious that I can almost guarantee it will become your go-to. The chocolate mousse tastes best if you eat it when it’s been refrigerated between 6 and 12 hours. After the 12-hour mark, the mousse becomes heavier and more dense.
In a large heat-resistant bowl set over a pan of simmering water, melt the chopped chocolate, stirring occasionally with a silicone spatula.
Meanwhile, wash and dry the bowl of your stand mixer so that it’s spotlessly clean. Using the whisk attachment, whisk the egg whites and lemon juice on medium speed until they form soft peaks. Increase to high speed and gradually add the sugar, whisking until the egg whites form soft peaks.
Whisk one-third of the egg whites into the warm chocolate, then immediately use a silicone spatula to fold in the remaining egg whites. This step must be done quickly, since you’re adding a cold mass to a hot mass and you don’t want the chocolate to solidify, which would result in grainy mousse. That’s why it’s important that the egg whites are at room temperature. Be careful not to overmix, or the mousse will lose its lightness.
Spoon into six glasses or ramekins, or into one big bowl, and let set in the fridge for 3 to 12 hours before serving.