Triple Chocolate Mousse Cake

If you like chocolate, then you will love this decadent dessert.  The cake is comprised of three distinct layers of chocolate, each one progressively lighter in color and flavor, all topped with a sprinkling of delicate dark chocolate curls.  To elaborate, the bottom layer is a rich, flourless dark chocolate cake.  This is topped with a rich and creamy dark chocolate mousse, and the top layer is a sweet and silky white chocolate mousse.

I first saw this recipe featured on an episode of America’s Test Kitchen, and I was totally smitten with it.  Unfortunately, I didn’t get around to making it until last weekend (about a year after seeing the episode.)  Do not make the same mistake I did and set this recipe aside only to be forgotten – I highly recommend making this cake as soon as possible.  In fact, I’m already planning to make it again very soon!

Triple Chocolate Mousse Cake

(print recipe)

Ingredients:

For the bottom layer:

  • 6 tbsp. (3/4 stick) unsalted butter, cut into 6 pieces, plus extra for greasing the pan
  • 7 oz. bittersweet chocolate, finely chopped
  • ¾ tsp. instant espresso powder
  • 1½ tsp. vanilla extract
  • 4 large eggs, separated
  • Pinch of table salt
  • 1/3 cup packed light brown sugar (2 ½ ounces), crumbled with your fingers to remove lumps

For the middle layer:

  • 2 tbsp. cocoa powder, preferably Dutch-processed
  • 5 tbsp. hot water
  • 7 oz. bittersweet chocolate, finely chopped
  • 1½ cups cold heavy cream
  • 1 tbsp. granulated sugar
  • 1/8 teaspoon table salt

For the top layer:

  • ¾ tsp. powdered gelatin
  • 1 tbsp. water
  • 6 oz. white chocolate, finely chopped (or white chocolate chips)
  • 1½ cups cold heavy cream

For the garnish: shaved chocolate curls or cocoa powder

Directions:

  1. For the bottom layer: Adjust an oven rack to the middle position and preheat the oven to 325 degrees.  Butter the bottom and sides of a 9 ½ -inch springform pan (the sides of the pan should be at least 3 inches high).  Melt the butter, chocolate, and espresso powder in a large heatproof bowl set over a pan of simmering water, stirring occasionally until the mixture is smooth.  Remove the mixture from the heat and let cool slightly, about 5 minutes.  Whisk in the vanilla extract and egg yolks; set aside.
  2. In a stand mixer fitted with the whisk attachment, beat the egg whites and salt on medium speed until foamy, about 30 seconds.  Add half of the brown sugar into the mixing bowl and beat until combined, about 15 seconds.  Add the remaining brown sugar and continue to beat at high speed until soft peaks form when the whisk is lifted, about 1 minute longer.  Using a whisk, mix one-third of the beaten egg whites into the chocolate mixture to lighten it.  Using a rubber spatula, gently fold in the remaining egg whites until no white streaks remain.  Carefully pour the batter into the prepared springform pan and gently smooth the top with an offset spatula.
  3. Bake until the cake has risen, is firm around the edges, and the center has just set but is still soft (the center of the cake should spring back after pressing gently with a finger), about 13-18 minutes.  Transfer the cake to a wire rack to cool completely, about 1 hour.  Do not remove the cake from the pan.
  4. For the middle layer:  Combine the cocoa powder and hot water in a small bowl and set aside.  Melt the chocolate in a heatproof bowl set over a saucepan filled with 1 inch of simmering water, stirring occasionally until smooth.  Once the chocolate has melted, remove it from the heat and cool slightly, about 2-5 minutes.  (Alternatively you can melt the chocolate in a heatproof glass bowl in the microwave.)
  5. In the clean bowl of a stand mixer fitted with the whisk attachment, whip the cream, granulated sugar and salt at medium speed until the mixture begins to thicken, about 30 seconds.  Increase the speed to high and whip until soft peaks form when the whisk is lifted, about 15-60 seconds.
  6. Whisk the cocoa powder mixture into the melted chocolate until smooth.  Using a whisk, fold one-third of the whipped cream into the chocolate mixture to lighten it.  With a rubber spatula, fold in the remaining whipped cream until no white streaks remain.  Pour the mousse into the springform pan over the cooled cake and gently tap the pan on the counter 3 times to remove any air bubbles.  Then carefully smooth the top with a spatula and wipe the inside edge of the pan with a damp paper towel to remove any drips.  Refrigerate the cake for at least 15 minutes while you prepare the top layer.
  7. For the top layer:  In a small bowl, sprinkle the gelatin over the water and let it stand at least 5 minutes.  Place the white chocolate in a medium bowl.  Bring ½ cup of the cream to a simmer in a small saucepan over medium heat.  Remove the pan from the heat, add the gelatin mixture, and stir until dissolved.  Pour the cream mixture over the white chocolate and whisk until the chocolate has melted and the mixture is smooth.  Cool the mixture to room temperature, stirring occasionally, about 5-8 minutes.  (The mixture should thicken slightly).
  8. In the clean bowl of a stand mixer fitted with the whisk attachment, whip the remaining one cup of cream at medium speed until it begins to thicken, approximately 30 seconds.  Increase the speed to high and whip until soft peaks form when the whisk is lifted, 15-60 seconds.  Using a whisk, fold one-third of the whipped cream into the white chocolate mixture to lighten it.  With a rubber spatula, gently fold in the remaining whipped cream until no white streaks remain.  Spoon the white chocolate mousse into the pan over the middle layer, and then smooth the top with an offset spatula.  Return the cake to the refrigerator and chill until set, at least 2½ hours.
  9. To serve:  Garnish the top of the cake with chocolate curls or dust the cake with cocoa powder.  Carefully remove the sides of the springform pan from the cake.  Cut the cake into slices and serve.

Serves: 12-16

Note:  I don’t have a 9 ½ inch springform pan.  Instead I used my 7-inch springform pan and halved the above recipe.  This worked perfectly, and yielded a smaller cake that serves 6-8 people.

Source: Adapted from Cook’s Illustrated magazine, November & December 2009 issue

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6 Responses to “Triple Chocolate Mousse Cake”


  1. 1 Rashi Gupta January 30, 2011 at 1:46 AM

    looks sinfully amazing. will definitely try this!

  2. 2 Kristine January 30, 2011 at 7:31 AM

    This cake looks so delicious- perfect for when a chocolate craving hits! I’ll have to try it sometime.

  3. 3 Dr. Dredd February 1, 2011 at 8:51 AM

    Do you recommend any particular brand of bittersweet chocolate?

  4. 6 Sues February 2, 2011 at 8:59 PM

    Oh wow, this looks just perfect!! Beautiful and delicious :) I totally love everything America’s Test Kitchen does!


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