For the dark chocolate truffle: Preheat the oven to 350 degrees F. Line a 9-inch cake pan with foil.
Grind the chocolate in a food processor. Place the ground chocolate and the sugar in a large mixing bowl. Slowly add the boiling water and stir until all the chocolate is melted. Using a whisk, incorporate the butter into the chocolate mixture well blended. Whisk in the eggs, then strain through sieve.
Pour the truffle mixture into the prepared pan. Bake until just set, 20 minutes. Chill for 4 hours.
For the chocolate mousse: Melt the chocolate and cool slightly. Whip the cream.
Put whole eggs and the egg yolks into a large bowl; whisk with an electric mixer to break up the yolks.
When the chocolate has cooled, add the whisked eggs and blend with hand mixer.
In a separate bowl, whip the egg whites.
Add one-quarter of the whipped cream to the chocolate mixture and mix with spatula, scraping the bowl until just incorporated. Add the remaining whipped cream and begin folding it in, scraping the bowl often. Halfway through, add the whipped egg whites. Fold everything together until well incorporated. Chill for 4 hours. (Makes filling for three 9-in cakes.)
For the banana cake: Preheat the oven to 350 degrees F.
Cream the butter, margarine and sugar with an electric mixer until very light and fluffy. Mix in the bananas. Slowly add the eggs, mixing until incorporated. Alternate adding the dry ingredients and the milk to the butter mixture, beginning and ending with the dry ingredients. Add the vanilla.
Fill two 9-inch cake pans halfway up with batter. Bake until the cake is set but still shiny on top, 20 minutes. Let cool.
To assemble the cake: Place the first layer of banana cake, top-side up, on a cake board. Add 2 large scoops (about 2 cups) of mousse and spread with a spatula. Take the truffle out of the pan, keeping the foil still on, and invert onto the mousse; remove the foil. Place 2 more large scoops of mousse onto the truffle and spread with a spatula. Invert the second banana cake onto the mousse.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.