6 ounces bittersweet or semisweet chocolate, chopped
4 ounces unsalted butter, cut into small pieces
3 tablespoons espresso, cooled
4 large eggs, separated
2/3 cup sugar, plus one tablespoon
2 tablespoons dark rum
1 tablespoon water
pinch of salt
1 1/2 cups whipping cream
1/2 teaspoon vanilla extract
Heat a saucepan one-third full with hot water, and in a bowl set on top, melt together the chocolate, butter and coffee, stirring over the barely simmering water, until smooth. Remove from heat.
Fill a large bowl with ice water and set aside.
In a bowl large enough to nest securely on the saucepan of simmering water, whisk the yolks of the eggs with the 2/3 cup of sugar, rum, and water for about 3 minutes until the mixture is thick, like runny mayonnaise.
Remove from heat and place the bowl of whipped egg yolks within the bowl of ice water and beat until cool and thick. Then fold the chocolate mixture into the egg yolks.
In a separate bowl, beat the egg whites with the salt until frothy. Continue to beat until they start to hold their shape. Whip in the tablespoon of sugar and continue to beat until thick and shiny, but not completely stiff, then the vanilla.
Fold one-third of the beaten egg whites into the chocolate mixture, then fold in the remainder of the whites just until incorporated.
In a separate bowl, beat the whipping cream until firm, then fold in the chocolate-egg white mixture, but don’t overdo it or the mousse will lose volume.
Transfer the mousse to a serving bowl or divide into serving dishes, and refrigerate for at least 4 hours, until firm.
(*This is Julia Childs’ recipe, but I changed things around a bit. Her original recipe can be found in Mastering the Art of French Cooking, of course.)