Place the chopped chocolate in a medium heatproof bowl.
Heat the brewed coffee in a small saucepan until just simmering. Pour the hot coffee over the chocolate and let it sit for 2 minutes without stirring.
Whisk the chocolate and coffee mixture until completely smooth. Whisk in the sugar and vanilla extract until combined. Set the bowl aside to cool to room temperature.
In a separate large bowl, use an electric mixer to beat the cold heavy whipping cream and salt until stiff peaks form. This creates the light, airy texture.
Gently fold about one-third of the whipped cream into the cooled chocolate mixture to lighten it.
Carefully fold the remaining whipped cream into the chocolate mixture in two additions until just combined. Do not overmix; stop when no white streaks remain.
Spoon or pipe the chocolate mousse into individual serving dishes or small glasses.
Chill the mousse in the refrigerator for at least 4 hours, or until firm.
Notes
For a deeper flavor, use dark chocolate with 70% cocoa content or higher.
If you prefer a mousse without eggs, this recipe relies on whipped cream for structure.
Serve this decadent chocolate mousse topped with fresh raspberries or chocolate shavings.