Chill your mixing bowl and beaters in the refrigerator along with the cream.

Break the chocolate bar into small pieces. Melt it using a double boiler.

Place the mascarpone in a mixing bowl. Mix it with the granulated sugar.

Once the chocolate is melted, fold it into the mascarpone mixture.

Pour the cream into the chilled bowl. Add the powdered sugar and beat with an electric mixer until stiff peaks form.

Fold half of the whipped cream into the mascarpone mixture. Mix and refrigerate.

Before serving, top the mousse with the remaining whipped cream and pralines.