In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer. Remove from heat and add the chocolate chips. Stir until the chocolate is completely melted and the mixture is smooth. Stir in the cooled brewed coffee and vanilla extract. Set aside to cool slightly.

In a separate bowl, beat the egg whites with a pinch of salt using an electric mixer until soft peaks form. Gradually add the granulated sugar and continue to beat until stiff peaks form.

Gently fold the cooled chocolate mixture into the beaten egg whites, being careful not to deflate the egg whites. Fold until just combined and no streaks remain.

Spoon the mousse into individual serving dishes or a large bowl. Cover with plastic wrap and refrigerate for at least 2 hours, or until set.

Serve chilled, optionally topped with whipped cream or chocolate shavings.