Chocolate-banana mousse cake

I wanted to make a cake for a while now but I did not know how to go about it. A few days ago I have sketched my idea of a cake in my notebook and then I have researched all of the recipes I needed to make my cake. I decided for a simple mousse cake because it is easy to make and does not require a lot of ingredients.
The flavors I chose were primarily chocolate and banana, the classic combination that most people love and are familiar with. This is one of my favorite combination of flavors and you really can't go wrong with it.

For the bottom of the cake I made a basic chocolate sponge. I never made any kind of sponge and this one is easy to make and it turned out great. Since I have no experience in making a sponge I found the original recipe for the chocolate sponge here. It is a simple and reliable recipe that works every time. The sponge is then soaked with a vanilla syrup, which makes it moist and extra flavorful.

On top of the sponge I made a vanilla mouse. The mousse is also simple to make, all you need to do is a basic cream anglaise (a light pouring custard made from eggs yolks, hot milk, sugar and vanilla), then you add gelatin and whipping cream and you are done.

There are many ways you can incorporate the banana flavor in a cake but I have decided to caramelize the bananas and spread them on top of the vanilla mousse. For a stronger banana flavor you can also make a banana mouse on top of the caramelized bananas. All you need for caramelized bananas is sugar, bananas, butter and a little cinnamon. The bananas are cooked until soft and delicious.

The final layer of the cake is a dark chocolate mousse. This mousse is made with two ingredients, chocolate and whipping cream. Because there is no egg or gelatin in this mousse it gets grainy after a few days in the fridge but I am sure that the cake will be gone from your fridge before that.

The most important thing when you are making the mousses is that you cool basic mixture for the mousse down before you fold in the whipping cream. If the mixture is still hot, the whipping cream will melt and you will have to start again.  

After the chocolate mousse is done it is spread on top of the caramelized bananas and you are done with the cake, just put it in the fridge to set. The cake will look great and the layers will be visible but if you would like a more polished look you can pour chocolate ganache or a chocolate glaze on top of the cake and cover it so that the layers of the cake will show only when you cut a piece.

Chocolate-banana mouse cake

(Makes 1 big(20cm) or 3 small (12cm) cakes)

Time:

Preparation: 20min

Cooking/Baking: 20min/15min

Cooling/Setting: 30min/2 hours
  

For the chocolate sponge:

• 3 eggs
• 90g granulated white sugar
• 70g plain flour
• 1/2 tea spoon baking powder
• 15g cocoa powder
• 20g melted butter
• 15g room temperature heavy cream
• a pinch of salt
• 1/2 tea spoon vanilla extract

For the syrup:

• 50ml water
• 3 table spoons granulated white sugar
• 1/2 tea spoon vanilla extract (optional)
• 1/4 tea spoon instant espresso powder (optional)

For the vanilla mousse:

• 100ml milk
• 30g granulated white sugar
• 1/2 vanilla pod
• 20g egg yolks (1 big yolk)
• 3g gelatin leaf 
• 140g whipping cream

For the caramelized bananas:

• 1 large banana or 2 small ones
• 3 table spoons granulated white sugar
• 1/4 tea spoon cinnamon (optional)
• 15g butter

For the chocolate mousse:

• 110g chocolate (I used dark chocolate)
• 40g whipping cream
• 170g whipping cream

Making the chocolate sponge:

Preheat the oven to 180°C (356°F). Line the 30cm x 30cm baking pan with parchment paper, if you do not have this type of baking pan you can use a smaller or wider type of a baking pan but this will affect the thickens and the baking time of the sponge. 

Combine flour, salt and cocoa powder in a bowl and set aside. In the bowl of your electric or hand mixer whisk the eggs until light and frothy. While whisking gradually add the sugar and whisk until the mixture becomes thick and pale.

Take 1/4 of the egg mixture and mix with the warm whipping cream and melted butter, fold to combine, set aside. Take the flour mixture and sprinkle into the 3/4 of the egg mixture and fold to combine. Pour the 1/4 egg mixture with the butter and the cream in to the bater with the flour. Fold to combine and pour in to the prepared baking pan. Bake the sponge for 14-16 minutes. Check if the sponge in baked with a toothpick. Insert the toothpick in the sponge and if it comes out clean it means that the sponge is done, if  the toothpick does not come out clean, bake the sponge for another minute and check again.

After the sponge is done baking, leave aside to cool. When the sponge is cool enough cut it into rounds and place it in the cake mold or dessert ring, set aside.

Making the simple syrup:

Combine water, sugar and espresso powder and boil until it thickens a little, pour in the vanilla extract. Set aside to cool. Brush the syrup generously on top of the chocolate sponge and set aside.

Making the vanilla mousse:

Put the gelatin in cold water and leave aside to bloom. In a small sauce pan bring the milk to a boil. In the meantime, combine the yolk, sugar and seeds from the vanilla pod (put the rest of the vanilla in with the milk for maximum flavor) in a heavy-bottom sauce pan and whisk to combine. When the milk boils, temper the egg yolks with a small amount of hot milk while whisking. Continue whisking and slowly pour the remainder of the milk into the tempered yolk mixture. 

Place the pan on medium heat and whisk until the mixture returns to a boil and thickens slightly. Take the pan of the heat and put in the gelatin, stir to combine, then strain the mixture into a bowl to remove any lumps or cooked egg. Cool the vanilla mixture by putting the bowl with the mixture in the bowl with cold water. Wait until completely cooled. It is important that the mixture is cool enough so that when you add the whipping cream the cream does not melt. Whip the cream until it forms soft peaks. Gently fold 1/3 of the whipping cream in to the vanilla mixture. 

Fold the rest of the cream into the mixture, don't worry the mixture will seem quite loose but it will firm up in the freezer. 

Pour the mousse on top of the prepared chocolate sponge and put the whole thing in a freezer.          

Making the caramelized bananas:

Put the sugar in a sauce pan on a medium heat. Slice the banana and put in with the sugar. Cook until it caramelizes and add the butter and cinnamon. Cook until the bananas become soft. Set aside to cool.

After the bananas have cooled down take the cakes from the freezer and, if the vanilla mousse in set and firm, arrange the bananas on top. Put in the fridge.

Making the chocolate mousse:

Chop the chocolate into small pieces and put in the heat-proof bowl. Boil the whipping cream (40g) and pour over the chocolate. Wait 2 minutes then stir until the chocolate is completely melted. If the chocolate does not melt completely, place the bowl over a pot of simmering water and gently heat the bowl until all the chocolate melts (here I burned my chocolate because I left the bowl on top of the pot for too long, so be careful :). Cool of the chocolate by putting the bowl with the chocolate in the bowl with cold water. Wait until completely cooled. Whip the remaining cream (170g) until soft peaks form. Pour 1/3 of the whipping cream and fold into the chocolate. Gently fold the rest of the whipping cream with the chocolate. Take the cakes out of the fridge and pour the mousse on top of the caramelized bananas. Refrigerate until the mousse is firm. 

When taking the cake out of the mold use a butter knife or a palette knife to scrape the edges around the cake mold. The cake should came out easily after that. You can decorate the cake in any way you like, I just sprinkled some colored sprinkles and added s few toasted pecans.
I hope you give this recipe a try and that you will enjoy making and eating this cake as much as I did.