It is important to use a SPRINGFORM pan throughout this recipe. Another option is to bake a cake and use adjustable cake rings to build up the mousse.
I have used a 9” round springform pan here.
Prepare the cake as per the recipe and instructions here.
Let it cool down completely before adding the mousse.
I like to prepare it a day ahead of time and store it wrapped in plastic wrap and foil. Leave it in the fridge or at room temperature until layered with mousse.
Preparing the cake pan for layering
Slice the top of the cake horizontally to level it flat and then add the mousse layer.
You can choose to keep a thin layer of cake by slicing it accordingly.
Enjoy the scrapes with tea or coffee or maybe make some cake pops.
Try using an acetate or parchment paper collar on the circumference of the inner side of the pan for smooth removal of cake later.
Prepare Semi-sweet chocolate mousse
Process of melting chocolate
Warm-up cream in a microwave-safe bowl or in a pot over a stovetop just until a simmer and not boiling hot.
Add in the semi-sweet chocolate chips and cover the bowl with a lid/ dish. Keep it undisturbed for 30 seconds. The trapped heat of the cream will slowly start to melt the chocolate.
Now open the lid and start stirring gently. It will look goopy at first but after a minute of stirring it will start to form a smooth chocolate sauce known as ganache.
If you suspect that all the chocolate didn’t melt then just pop it in the microwave for 10 seconds at a time. Smoothen out the tiny bits of chocolate and keep the ganache aside to cool at room temperature.
Whipping chilled heavy whipping cream
Meanwhile in a big bowl add cream, a pinch of salt, and vanilla. Whip it with an electric or handheld whisk for 4-5 minutes. Or until you see that the cream has started to just thicken. Now switch off the electric whisk and just manually whisk it to a super soft consistency. Whisking with a hand, later on, gives you more control over the consistency and avoids over-whipping the cream.
We are looking for a very soft peak consistency. Refer to the video for better understanding. Please do not whisk until stiff peaks. The cream should be just thick and not hold the peaks at all.
Mixing process to make the mousse
The chocolate should have come to room temperature by now. It should not be warm.
Now scoop 3-4 tablespoons already whipped cream into chocolate first. Fold it gently so that the cream is completely incorporated with chocolate. This is done to stabilize chocolate. It is a crucial step taken to avoid chocolate seizing when it comes in contact with chilled cream.
The next step is adding the chocolate mixture to the big bowl of already whipped cream. Fold it gently in one clockwise direction. We want the mouse light and fluffy. This way we are incorporating air in the mousse.
Once it is mixed well, add it to the prepared cake pan. Level the top with a spatula as much as you can. It does not have to be perfect. Loosely cover it with foil and chill in the refrigerator (not the freezer).
Prepare White Chocolate Mousse
Important - Follow the sequence – 1st whip the cream and set it aside. 2nd – activate the agar-agar. 3 rd – Melt the white chocolate. You can do the 2nd and 3rd steps simultaneously using two stove-top.
Whip heavy whipping cream
Same as you would do for semi-sweet chocolate mousse. Just repeat the process.
In a big bowl add cream, a pinch of salt, and vanilla. Whip it with an electric or handheld whisk for 4-5 minutes. Or until you see that the cream has started to thicken. Now switch off the electric whisk and just manually whisk it to a super soft consistency. Whisking with a hand, later on, gives you more control over the consistency and avoids over-whipping the cream.
We are looking for a very soft peak consistency. Refer to the video for better understanding. Please do not whisk until stiff peaks. The cream should be just thick and not hold the peaks at all.
Activate agar agar
Add agar-agar to a bowl of cream. Mix well to combine. Heat this mixture on medium heat stirring frequently. Once the mixture comes to a boil let it cook for a minute. Switch off the flame and let it cool to warm.
Make the white chocolate ganache
I recommend using the double boiler method to melt white chocolate and not the microwave. White chocolate is very delicate and tends to burn in the microwave.
Melt the cream and white chocolate using the double boiler method over the stovetop.
Once it is silky smooth take the bowl off the stove and let the chocolate cool completely. The white chocolate will thicken as it cools but it should still be flowy consistency.
Make the mousse - Work quickly
Now place the chilled whipped cream, agar-agar mixture, and white chocolate on your work table.
Then scoop 3-4 tablespoons already whipped cream into the white chocolate first. Fold it gently so that the cream is completely incorporated with chocolate. This is done to stabilize chocolate. It is a crucial step taken to avoid chocolate seizing when it comes in contact with chilled cream.
If you think chocolate is turning gritty then just add some more cream, it will turn smooth again.
The next step is adding the white chocolate mixture to the big bowl of already whipped cream. Fold it gently in one clockwise direction until mixed, say for 20 seconds.
Now add in the agar agar mixture. Make sure it is warm and flowy. It should not set before mixing. If you suspect that the mix is thickened, set, or cooled before adding it to the cream then warm it again on low heat until flowy consistency.
The next step is to work quickly. Immediately add the agar cream mixture into the white chocolate whipped cream mixture and whip for 10-15 seconds, making sure it is blended well. Do not overwhip.
Pour it over the semi-sweet mousse layer. Level as much as you can. Place it in the fridge to set for at least an hour before you layer it with ganache.
Making top ganache layer (Optional)
Place semi-sweet chocolate in a medium-sized bowl. Warm-up cream in a microwave-safe bowl or in a pot over a stovetop just until a simmer and not boiling hot.
Pour it over the chocolate chips and cover the bowl with a lid/ dish. Keep it undisturbed for 30 seconds. The trapped heat of the cream will slowly start to melt the chocolate.
Now open the lid and start stirring gently. It will look goopy at first but after a minute of stirring it will start to form a smooth chocolate sauce known as ganache.
If you suspect that all the chocolate didn’t melt then just pop it in the microwave for 10 seconds at a time. Smoothen out the tiny bits of chocolate and keep the ganache aside to cool at room temperature.
Assembling the cake and garnish
Once the ganache has cooled down pour it over the white chocolate layer and swirl it to cover the top of the cake. Place it in the fridge to set overnight or at least 8 hours before garnishing.
You may add some chocolate shards, shavings, curls, and berries to decorate the cake.
Video
Notes
This recipe makes around 2.5-kilo cake.As this recipe has a lot of steps please go through the video and post a couple of times before starting. It may seem overwhelming but it is very easy. Just follow the sequence.
Possible substitutes
Use parchment instead of an acetate sheet to cover the collar round of the cake. It will aid easy removal later on. If you do not have either of them then, simply run a knife around the circumference to loosen the edges.
I have used heavy whipping cream throughout the recipe. Look for a carton that says heavy whipping cream and not just heavy cream.
There is no substitute for agar-agar. It is crucial to set the white chocolate mousse part.
I have used agar-agar powder.
This cake recipe is not overly sweet.
You can use bittersweet or dark chocolate instead of semi-sweet if desired.
Skip the top ganache layer but I highly recommend it.
I have kept the decoration very simple, use your imagination and decorate as desired.
You may skip the white chocolate layer and simply double the recipe for semi-sweet chocolate mousse.
Important tips to make the best mousse cake
Do not whip the cream until still peaks. Keep it to very soft loose peaks.
For the white chocolate mousse part -Follow the sequence as mentioned. Remember to 1st whip the cream and set it aside in the fridge. 2nd – activate the agar-agar. 3rd – Melt the white chocolate.About agar-agar – things to keep in mind
Add agar-agar to cold or room temperature cream. Do not add it to warmed cream as it will clump up. Warm up the cream after adding agar-agar, not before that.
Do not let the agar cream mixture cool down before adding to the whipped cream. It should be warm and flowy consistency or it will set in clumps before whipping.
After whipping everything you may sometimes find very tiny bits of agar, it is completely fine and won’t affect the final taste or texture.
Chill the entire cake in the fridge for at least 6-8 hours to set.
Storage and Shelf life of this mousse cake
Triple chocolate mousse cake needs to be refrigerated at all times and served chilled.
At a party, you can keep this cake out at the venue for 3-4 hours but in a cool place away from sunlight.
This cake keeps well in the fridge for 4-5 days.
Make ahead of time tips
Make the chocolate cake base up to 2 days in advance to store in the fridge or 3 months in advance and store it in the freezer. When you are ready to make the cake thaw it for 2-3 hours at room temperature.
Make ganache up to 1 week in advance. When you are ready to use it, just warm it up to get to a pourable consistency.
Make chocolate mousse up to 2 days in advance and store them in separate airtight containers.