Melt bittersweet chocolate in a double boiler (or in a bowl placed on top of a pot of boiling water). Once chocolate is fully melted, add the yolks slowly, constantly mixing while adding.

Meanwhile, beat the egg whites. When almost stiff, add confectioner’s sugar and continue beating until stiff peaks form.

Dissolve coffee and sweetener in boiling water. Add the dissolved coffee into the chocolate mixture and combine well.

Fold the chocolate mixture into the whites until just combined. Place in individual glass cups or dessert bowls. Place in the freezer.

Once mousse has frozen, make the topping by melting the chocolate in a double boiler. Once melted, add the dessert whip and stir to combine. Pour over frozen mousse and freeze again. Before serving, you can garnish with nuts and white chocolate.