Instructions

1. Fill a large saucepan with an inch or two of water and set it over medium heat until water comes to a low simmer. Place a medium bowl over the simmering water and place chocolate inside. Stir gently until chocolate is fully melted. Once fully melted, whisk the butter into the melted chocolate, 1 tablespoon at a time. Remove chocolate mixture from heat. Stir in the salt, vanilla, and coffee until completely incorporated. Whisk in yolks, one at a time, making sure that each is fully incorporated before adding the next. Set chocolate mixture aside
2. Stir egg whites in a clean mixing bowl set over a saucepan of hot water until slightly warm, 1 to 2 minutes; remove bowl from saucepan. Beat with an electric mixer set at medium speed until soft peaks form. Raise mixer speed to high and slowly add sugar, beating to soft peaks. Whisk a quarter of the beaten whites into chocolate mixture to lighten it, then gently fold in remaining whites
3. In a separate bowl, whip the heavy cream to soft peaks. Gently fold into mousse. Spoon portion of mousse into six to eight individual serving dishes or ramekins. Cover with plastic wrap and refrigerate to blend flavors, at least 2 hours, before serving
4. Optional: When ready to serve, whip heavy cream on high speed in a clean bowl until stiff peaks form.  Serve chocolate mousse with a dollop of whipped cream and a sprinkle of chocolate shavings