Place the chopped chocolate in a large heatproof bowl. Set aside.

In a large bowl, using a handheld electric mixer, beat the egg yolks and granulated sugar on medium-high speed until thick, smooth, and deeply yellow. Set aside.

In a medium saucepan over medium heat, warm 2 and 1/2 cups of the cream just until it comes to a simmer.

Remove the pan from heat and slowly whisk half of the hot cream into the egg yolk/sugar mixture, whisking constantly.

Transfer the tempered cream mixture back to the pan (with the remaining cream) and cook over medium heat, stirring constantly, until thick enough to coat the back of a spoon, about 5 minutes.

Pour the warm mixture over the chopped chocolate. Stir until smooth, then whisk in the vanilla, espresso powder, and salt.

Cover with plastic wrap and refrigerate until cold, about 1 to 2 hours.

Once the chocolate mixture is chilled, beat the remaining 1 and 1/2 cups of heavy cream with an electric mixer until stiff peaks form.

Gently fold the whipped cream into the chocolate mixture until evenly combined.

Spoon mousse into dessert cups, top with whipped cream and chocolate shavings, and serve immediately.

In a large bowl using a handheld electric mixer, beat the heavy cream and confectioners? sugar until medium-stiff peaks form.

Spoon the whipped cream on top of the mousse, add chocolate shavings, and serve.