Triple Chocolate Mousse Cake - originally posted on Sep 16/12

I first saw this amazing cake on America’s Test Kitchen-one of my favourite cooking shows.  It’s not a slick, Food Network style cooking show, but their approach to food is truly passionate and scientific.  This is the kind of dessert I dream about and I’ve been dying to try this recipe.  Yesterday I finally did and Mary declared “this is the best dessert I’ve had in my life”  I must say it’s pretty spectacular.  I am looking forward to making it again.
This is a special occasion cake.  Why?  Because it is time consuming-three layers are created and assembled, but if you plan ahead, you could make one layer per day and it would not take up half your Saturday.   Also, it’s expensive-butter, chocolate and cream are pricey ingredients.   Each layer stands on it’s own; a flourless chocolate cake recipe and 2 variations on chocolate mousse technique.  Rich, creamy and sweet, this is not an ‘every day’ cake.  Enjoy!
For the bottom layer:
6 tbsp.  butter, cut into pieces
7 oz. bittersweet chocolate, finely chopped
1 tsp. Ground coffee beans
1½ tsp. vanilla extract
4 large eggs, separated
Pinch of salt
1/3 cup light brown sugar

Butter the bottom and sides of a 9-inch springform pan. (I lined the bottom of the pan with a parchment round for easy removal later.) Combine the butter, chocolate, and coffee in the top of a double boiler, stirring occasionally until the mixture is smooth. Remove from the heat and let cool slightly, about 5 minutes. Whisk in the vanilla and egg yolks. Set aside.

Beat the egg whites and salt on medium speed until foamy, about 30 seconds. Crumble half of the brown sugar into the mixing bowl with your fingers to remove any lumps. Beat until incorporated, about 15 seconds. Add the remaining brown sugar and continue to beat on high speed until stiff peaks form, about 1 minute more.

Using a whisk, mix one-third of the beaten egg whites to the chocolate mixture to lighten it. Fold in the remaining egg whites gently with a rubber spatula until no streaks remain. Pour the batter into the prepared springform pan and smooth the top with a spatula.

Bake at 325 F about 15 minutes, until the cake has risen, is firm around the edges and the center has just set but is still soft (should spring back after pressing gently with a finger). Transfer the cake to a wire rack to cool completely, at least 1 hour. Do not remove the cake from the pan. (If not making the second layer right away, cover with plastic wrap and refrigerate until ready to proceed.)

For the middle layer:
2 tbsp. cocoa powder
5 tbsp. hot water
7 oz. bittersweet chocolate, finely chopped
1½ cups whipping cream
1 tbsp. sugar
Pinch of salt
Whisk together the cocoa powder and hot water in a small bowl; set aside. Melt the chocolate in the top of a double boiler, stirring occasionally until smooth. Once melted, remove from the heat and let cool slightly, 2-5 minutes.

Whip the cream, sugar and salt on medium speed until the mixture begins to thicken, about 30 seconds. Increase the speed to high and whip until soft peaks form, Whisk in the cocoa powder mixture until smooth. Using a whisk, mix one-third of the whipped cream to the chocolate mixture to lighten it. Fold in the remaining whipped cream gently with a rubber spatula.  If there are a few streaks, that's ok.
Pour the mousse into the springform pan over the cooled cake and tap gently on the counter 3 times to remove air bubbles. Gently smooth the top with a spatula. Wipe the inside edge of the pan to remove any drips. Refrigerate for at least 15 minutes while preparing the top layer.


For the top layer:
¾ tsp. powdered gelatin
1 tbsp. water
6 oz. white chocolate, finely chopped
1½ cups heavy cream
Sprinkle the gelatin over the water in a small bowl and let stand at least 5 minutes to soften. Place the white chocolate in a medium bowl.

Bring ½ cup of the cream to a boil in a small saucepan. Remove the pan from the heat, add the gelatin mixture and stir until dissolved. Pour the hot cream mixture over the white chocolate and let stand about 1 minute. Whisk until the mixture is smooth. Cool to room temperature, about 5-8 minutes, stirring occasionally.
Whip the remaining 1 cup of cream until soft peaks form when the whisk is lifted.  Using a whisk, mix one-third of the whipped cream to the white chocolate mixture to lighten it. Fold in the remaining whipped cream gently with a rubber spatula until no streaks remain. Spoon the white chocolate mousse into the pan over the middle layer. Smooth the top with an offset spatula.

Return the cake to the refrigerator and chill until set, at least 2½ hours.

You could decorate with shaved chocolate, chocolate curls or a dusting of cocoa powder.  Raspberries would also be delicious with this dessert.