Classic Chocolate Mousse

Directions

1. 1
   Beat 1/2 cup cream in a medium bowl until stiff peaks form; cover and chill.
2. 2
   Combine egg yolks, espresso, salt, and 2 tablespoons sugar in a large metal bowl. Set over a saucepan of gently simmering water (do not allow bowl to touch water). Cook, whisking constantly, until mixture is lighter in color and almost doubled in volume and an instant-read thermometer inserted into the mixture registers 160°F, about 1 minute.
3. 3
   Remove bowl from pan. Add chocolate; whisk until melted and smooth. Let stand, whisking occasionally, until room temperature.
4. 4
   Using an electric mixer, beat egg whites in another medium bowl on medium speed until foamy. With mixer running, gradually beat in remaining 1 tablespoon sugar. Increase speed to high and beat until firm peaks form.
5. 5
   Fold egg whites into chocolate in 2 additions; fold whipped cream into mixture just to blend.
6. 6
   Divide mousse among six teacups or 4-ounce ramekins. Chill until firm, at least 2 hours. DO AHEAD:
7. 7
   Before serving, whisk remaining 1/4 cup cream in a small bowl until soft peaks form; dollop over mousse.