Triple-Layer Chocolate Mousse Cake

I made this last weekend for the department Christmas party. It got enough rave reviews to make it seem like a good kickoff post for TasterThoughts. I got the recipe from the King Arthur Flour Baker's Companion (a cookbook that I highly recommend! [In the interests of full disclosure, my mom works for the King Arthur Flour company, but I am not affiliated with them, and the company has no association with this blog.]).

This looks really long, but it's easy.

One note on the recipe -- if you bake it in a water bath & some water gets into the pan, as long as it's just a little water, I wouldn't worry. I had some water seep in and I had to bake the bottom layer a little longer (35 minutes instead of the 26-28 minutes called for) before a cake tester came out clean, but other than that, I don't think it made a big difference. (At one point in making it, I seriously considered throwing it out because I got water in it, and making something else. I'm glad I didn't do that, in retrospect. :) )


Also, the cake layer calls for bittersweet or semisweet chocolate. I used bittersweet.

Anyhow, here's the recipe:

Three-Layer Chocolate Mousse Cake
(from The King Arthur Flour Baker's Companion)

One Cake, at least 16 servings

This deep, dark chocolate cake, which features milk chocolate mousse topped by raspberry, white chocolate mousse, is a risk to your waistline -- but it's worth every bite! While the directions may seem a bit long, the only hard part is forcing yourself to take the time to be sure the ingredients are at the proper temperature. Don't try to rush the melting of the chocolate by microwaving it on high power; don't forget to let the chocolate mixtures cool to lukewarm before adding the whipped cream; and don't try to rush the cooling by putting the chocolate in the refrigerator. Also, don't skip warming the eggs. These are all seemingly little steps that can make a big difference in how the finished product turns out. This cake serves 16 people, but after a rich dinner the slices could be made thinner to serve even more.

CAKE
10 oz. (about 1 2/3 cups chopped) bittersweet or semisweet chocolate*
4 large eggs (at room temperature), separated
1/3 c. (2 1/4 oz.) sugar
1/8 tsp. salt
1 tsp. vanilla extract
8 tbsp. (1 stick, 4 oz.) soft butter**

MILK CHOCOLATE MOUSSE
10 oz. (about 1 2/3 cups chopped) milk chocolate
1 1/2 c. (12 oz.) heavy cream (not whipping cream, and preferably not ultra-pasteurized)
1 tsp. unflavored gelatin softened in 2 tbsp. cool water, or 2 sheets gelatin soaked in cool water

RASPBERRY WHITE CHOCOLATE MOUSSE
5 oz. (about 1 scant cup, chopped) white chocolate
1/2 c. (4 oz.) raspberry purée (about 1 c. fresh or frozen berries, mashed or blended, seeds left in)
1 tsp. unflavored gelatin softened in 2 tbsp. cool water, or 2 sheets gelatin soaked in cool water
1 c. (8 oz.) heavy cream

GARNISH
Fresh raspberries and mint leaves

Preheat the oven to 350°F. Prepare a 9- or 10-inch springform pan by lightly greasing the bottom. Cut a circle of waxed paper or parchment to fit the bottom of the pan and place it in the pan. If you have Magi-Cake Strips, wet them and wrap them around the pan. If you don't have Magi-Cake Strips, the cake should be baked in a water bath (pan of hot water) so the edges don't dry out. If you're using the water bath, wrap the pan in two layers of aluminum foil so no water will seep in while the cake is baking.

FOR THE CAKE
Chop the chocolate into small chunks. Melt it slowly over very low heat -- in the top of a double boiler or, the easiest method, in a microwave. If you use the microwave, start with 1 minute at medium power, let the chocolate sit for several minutes, stir, then continue microwaving in increments of 15 to 20 seconds on medium to low power, stirring often. (Chocolate will burn fairly easily, and since it's an expensive ingredient, taking a few extra minutes to melt the chocolate slowly is worth it.) When most of the chocolate is fluid, set the bowl aside or remove the pan from the heat, and stir occasionally; the residual heat will finish the job for you.

While the chocolate finishes melting, place the room-temperature egg whites (if eggs are cold, warm them in a bath of hot water from your tap for 5 minutes) in a large mixing bowl and add about a third of the sugar. Using an electric mixer, start beating on slow speed, gradually increasing the speed. Beat until the whites are beginning to look fluffy. Add the remaining sugar, salt and vanilla and continue to beat until the sugar has dissolved and the meringue is shiny.

Next, using a whisk, stir the soft butter into the melted chocolate. If the butter is too cold, it will cause the chocolate to lump; if this happens, heat the mixture very briefly. When the butter is totally incorporated into the chocolate, whisk in the egg yolks.

Using a wire whisk, fold half of the meringue into the chocolate mixture. Fold in the remaining meringue with a rubber spatula, being sure to mix in the heavier batter at the bottom of the bowl.

Pour the batter into the prepared pan. Place the cake into the oven. Note: if you're using a water bath, the water should be hot when the pan is placed into it, and it should come about 1 1/2 inches up the side of the pan. Bake the cake for 26 to 28 minutes. The top will be shiny, and a cake tester inserted into the center will come out clean; however the cake won't spring back when touched in the center.

Remove the cake from the oven and let it cool for 1 hour; as it cools, it will sink and lose about a quarter of its volume; that's okay. Refrigerate the cake for another hour, then run a knife around the edge of the pan and invert the cake onto a plate. Remove the bottom of the pan and the paper, place the cake on a serving plate, and replace the ring from the springform around the cake; it will be the mold for the two mousses.

FOR THE MILK CHOCOLATE MOUSSE
Chop the milk chocolate, and place it in a microwave-safe bowl or the top of a double boiler. Bring 1/2 cup of the heavy cream to a boil and pour it over the chopped chocolate. Stir the chocolate and cream mixture until smooth; if the chocolate doesn't melt completely, heat it briefly in the microwave, or over very low heat in a double boiler.

While the chocolate is melting, soften the gelatin. Once the gelatin has softened, heat it over low heat or in the microwave, stirring to dissolve. When the gelatin mixture is completely free of lumps, stir it into the melted chocolate. In a medium-sized mixing bowl, whip the remaining 1 cup of heavy cream, being very careful not to overwhip it. It should just hold a soft peak. Check the chocolate mixture. It must be free of lumps and the temperature should be about 80°F -- warm enough to keep the chocolate from setting up, but not so hot the whipped cream melts when it's whisked in. Add about half of the whipped cream to the chocolate and whisk and fold as you did while making the cake, folding in the remaining whipped cream once the first half is whisked in. When the chocolate and cream are evenly blended, pour the mousse over the top of the cooled cake in the ring. Use an offset spatula to smooth the top. Return the cake to the refrigerator.

FOR THE RASPBERRY WHITE CHOCOLATE MOUSSE While the chocolate mousse is setting up, prepare the raspberry mousse. Melt the white chocolate very slowly, in a microwave or double boiler set over low heat. Heat the raspberry purée to warm and mix it into the white chocolate. It may look curdled as you first begin to stir, but will smooth out as you add more purée.

Soften the gelatin as directed for the chocolate mousse, then add it to the raspberry-white chocolate mixture. Whip the cream as directed previously, being careful not to overwhip it. Check that the white chocolate-raspberry mixture is warm to the touch, but not hot. Whisk it briefly, then fold it into the whipped cream. Pour the raspberry mousse over the milk chocolate mousse, smoothing the top. Refrigerate several hours before serving.

TO SERVE
Remove the ring by running a thin knife around the edge of the pan, then open the lock and lift it off. Hold an icing spatula or dinner knife perpendicular to your work surface and run it around the edge of the cake, smoothing it and removing any excess mousse that may have oozed out and smeared the layers. Slice the cake with a wet knife, wiping it off between slices; this will ensure a pretty presentation. Place the cake slices on plates garnished with a few fresh raspberries and a mint leaf.

This dessert may be made ahead and frozen for up to several weeks. Or you can prepare just the cake layer and freeze it, filling it the day you're going to serve it.

NOTE: Either of these mousses makes very good filling for cream puffs or a sponge cake.

* We don't recommend using inexpensive store-bought chocolate chips, as many have a stabilizer that may give the cake a slightly grainy mouth feel. We suggest you use a strongly flavored, high-quality couverture chocolate.

** The butter should be at warm room temperature, looking as if it's almost (but not quite) Ready to melt.

Nutrition information per serving (1 serving = 1 slice, 1/16 of cake, 103g)
399 cal | 28g fat | 5g protein | 6g complex carbohydrate | 27g sugar | 2g dietary fiber | 99mg cholesterol | 150 mg sodium | 183 mg potassium | 161RE vitamin A | 3mg vitamin C | 1mg iron | 67mg calcium | 105mg phosphorus | 11mg caffeine