This simple, not-too-sweet mousse is adapted from Joy’s 1963 edition. If using pasteurized eggs, they will require more whipping to form stiff peaks.

Stir together in a small saucepan over low heat until dissolved:

Melt in a double boiler or a heatproof bowl set over a pan of barely simmering water:

When the chocolate is melted, whisk in:

Gradually whisk the rum syrup into the chocolate until smooth. Let cool. Beat in a medium bowl until stiff but not dry:

Fold one-third of the egg whites into the chocolate, then fold in the remaining whites. Whip in a separate bowl until firm peaks form:

Fold the whipped cream into the chocolate mixture. Divide among 6 glasses or cups and refrigerate for at least 2 hours before serving.