Taken from The Taste of Belgium

Chocolate Mousse

150g bittersweet chocolate chopped into small pieces
4 tablespoons brewed coffee
4 large egg whites, at room temperature
2 tablespoons icing sugar
4 tablespoons whipping cream, well chilled
1 teaspoon dark rum, cognac or Grand Marnier (optional)
Chocolate shavings or whipped cream for garnish

Place the chocolate and coffee in the top of a double boiler over, but not touching, lightly simmering water. Stir occasionally with a wooden spoon until melted. Remove from the heat and let cool slightly.

Beat the egg whites until they hold soft peaks. Gradually beat in the sugar and continue to beat until the egg whites hold stiff peaks. Be careful not to overbeat or your egg whites will be too dry. In a separate bowl, beat the heavy cream until it forms soft peaks. Use a spatula to delicately  fold the egg whites into the chocolate in 3 additions, then, carefull fold in the whipped cream and the rum, if using.

Spoon the chocolate mousse into 4 champagne flutes , wine glasses or ramekins. Cover tightly with clingfilm and refrigerate for a few hours to let the mousse stiffen up. Before serving, garnish with some chocolate shavings, or pipe with some rosettes of whipped cream, using a piping bag with a star tip.