Step 1

Break up or chop the chocolate and place it in a heatproof bowl. Set the bowl over a saucepan of barely simmering water and allow the chocolate to melt, stirring occasionally. Once the chocolate has melted, remove it from the heat and let cool until tepid.

Step 2

In the meantime, put the egg yolks in a large bowl. In the bowl of a stand mixer fitted with the whisk attachment, or in a large bowl, using a handheld mixer, whip the egg whites to very firm peaks, about 5 minutes.

Step 3

When the chocolate has cooled, pour it into the bowl with the egg yolks and whisk well. Using a rubber spatula, stir in about one-third of the egg whites to lighten the mixture. Carefully spoon another third of the egg whites on top of the chocolate mixture and gently fold them in (do not stir). Add the remaining whites, folding just until the egg whites are incorporated.

Step 4

Spoon the mixture into ten 4- or 5-oz. (120- or 150-ml) ramekins or small coffee cups. Refrigerate for at least 2 hours, or overnight, until set.

Step 5

Serve the chocolate mousse cold, decorated with chocolate shavings, if desired.