9 ounces dark chocolate, chopped
8 ounces chocolate sauce
1 large egg
5 large egg yolks
1/2 cup sugar
2 ounces water
1 2/3 cups heavy whipping cream
1 chocolate cake (your favorite recipe)
1 cup whipping cream
1 tablespoon sugar
1 teaspoon vanilla
Melt the chocolate over a double boiler until completely smooth; remove and cool to room temperature. Meanwhile, combine the eggs and beat for 7 minutes on medium-high speed. In a small sauce pan, cook the sugar and water until 250 degrees using a candy thermometer. Remove the sugar from the stove and pour into egg mixture; beat for another 2 to 3 minutes. Let egg and sugar mixture cool to room temperature. Beat the whipping cream until soft peaks. Gently fold the egg mixture into the whipping cream. Then add the melted chocolate to the whipped cream, gently mixing it until the absence of streaks.
To make the crème chantilly, whip the cream until it forms soft peaks, then add the sugar and vanilla; mix until firm peaks are formed. Refrigerate. To make the layered cake, slice the cake into thin layers and add the mousse between the layers. Let the cake set in the refrigerator for several hours and serve with chocolate sauce, crème Chantilly, and a dusting of chocolate powder.