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For obvious reasons, I haven’t made many fancy cakes this past year. It’s hard to work up the enthusiasm when sharing celebrations with your extended family and friends isn’t an option (Zoom doesn’t count). But this week was my husband’s birthday, his second pandemic one. And even if the days of the past year have crawled along ever so slowly (especially lately — pandemic fatigue is real, I tell you), it still felt necessary to acknowledge their passing. With cake.
There’s a recipe called David’s Chocolate Raspberry Cake in my book. It’s his favorite, the classic combination of deep chocolate cake, bright raspberries, and silky chocolate frosting. He would have been more than happy with that, but I was in the mood for a Project. I didn’t dare stray from the chocolate-raspberry flavor combination, so this was all about repackaging. We start with the same chocolate cake, but this time the raspberry shows up an an intense gelée, a smooth crémeux (basically a fancy set pudding), and in the rich chocolate mousse. All of that is doused in a gloriously shiny glaze and sprinkled with chocolate crumbs (which taste like oreos) for texture. It was good, very good.
Tips for making mousse cakes
It’s all about the timing
Layered mousse cakes look impressive and complicated, but they aren’t necessarily more difficult to assemble than a “regular” layer cake. While there are several components, none are difficult to prepare and most can be made ahead of time. I suggest spreading the work out over a few days to keep the process relaxed and fun. For example, this is the schedule I followed:
- Day 1: Make chocolate cake (store in fridge), gelée (freeze), and crémeux (freeze)
- Day 2: Make chocolate crumbs, chocolate mousse, and assemble cake (freeze overnight)
- Day 3 (serving day): Make glaze, glaze and decorate frozen cake, defrost in fridge, eat!
You can definitely condense the project into 2 days. However, the key timing points are to make sure the gelée/crémeux are frozen before assembly, the mousse is used right before assembly, and the entire cake is frozen before glazing. Once glazed, the cake will need at least 2 hours in the fridge to defrost before eating.
There are a few pieces of equipment that make assembling mousse cakes straightforward and produce sleek results.
- Cake ring: Mousse cakes are often assembled in stainless steel rings that act as molds. I used a 6×3 cake ring.
- Acetate: Also known as cake collars, these thin, transparent sheets line the cake ring and make the frozen cake easy to unmold. I used 3″ high acetate cut to fit the ring.
- Instant-read digital thermometer: Important for the crémeux and mirror glaze, which are cooked or cooled to exact temperatures for best results. My favorite is the Thermapen.
- Immersion blender: Not strictly necessary, but does help remove lumps from mirror glaze for a smooth finish. I use this Hamilton Beach immersion blender.
- Powdered gelatin: Gelatin is the setting agent in several layers. I generally use powdered because it’s readily available in my area. You’ll need 26g total (if you’re using packets, this is a little less than 4 packets).
- Ruby chocolate: Ruby chocolate is a special variety of chocolate that is naturally pink. It has a unique fruity flavor that pairs really well with raspberries. I use Callebaut brand.
- Raspberry puree: You will need 260g raspberry puree total for all the components. You can buy pre-made puree online from some specialty baking / food stores, or make your own. To make raspberry puree, I simply blended one 400g bag of frozen raspberries (after thawing). I used puree with seeds for the gelée, but strained out the seeds for the crémeux and mousse. I had just enough puree; so if you want to use all seedless I would start with ~550g frozen raspberries to ensure you have enough after straining.
- Before making the dark chocolate raspberry mousse, I recommend having your cake and gelée-crémeux layers trimmed and all your equipment for assembly ready to go. The gelatin in the mousse will begin setting as soon as you add the cream, and the longer you wait the harder it will be to spread.
- I had intended to use another layer of cake but didn’t have quite enough room on after adding the gelée and crémeux. Next time I make this, I’ll put the first round of cake directly on the bottom of the cake ring and pipe mousse around it. That should give just enough room for another extra cake layer.
- I didn’t use a piping bag to add the mousse and ended up missing a couple spots around the crémeux. I filled them in with some ganache before glazing, and that worked ok. But after about a day in the fridge the glaze sort of wrinkled where the ganache was (probably because it was a different density compared the mousse). So I definitely recommend using a piping bag and taking care to get all the edges filled with mousse for the cleanest finish!
- The recipe for chocolate crumb makes quite a lot; feel free to cut in half or even a quarter depending on how much you want to use for garnish. I made a full batch to freeze extras for snacking and other projects.
Chocolate and Raspberry Mousse Cake with Dark Chocolate Mirror Glaze
Makes one 6×3 mousse cake (serves 8-12) | Chocolate cake recipe adapted from Baked to Order; raspberry gelée, dark chocolate raspberry mousse, and dark chocolate glaze adapted from Dominique Ansel’s Everyone Can Bake; ruby raspberry crémeux adapted from Felicia Mayden; chocolate crumb adapted from Milk
For the chocolate cake (Makes one 8″ round):
- 57g unsalted butter, cubed
- 27g neutral vegetable oil
- 60g whole milk
- 1 tsp vanilla extract
- 125g all-purpose flour
- 34g Dutch-processed cocoa powder
- 165g light brown sugar
- 1/2 tsp kosher salt
- 3/4 tsp baking soda
- 80g sour cream, at room temperature
- 1 large egg, at room temperature
- 60g freshly brewed coffee
For the raspberry gelée (makes about 240g or 1 cup):
- 20g cold water
- 4g (scant 1 1/4 tsp) powdered gelatin
- 185g raspberry puree (with or without seeds)
- 30g granulated sugar
For the ruby raspberry crémeux (makes about 435g or 1 3/4 c):
- 140g heavy cream (35%), divided
- 3g (1 tsp) powdered gelatin
- 115g ruby chocolate, chopped
- 20g corn syrup
- 1 egg yolk
- 100g whole milk
- 40g seedless raspberry puree
For the chocolate crumb (makes about 350g or 2 1/2 c):
- 105g all-purpose flour
- 4g (1 tsp) cornstarch
- 100g granulated sugar
- 65g Dutch-processed cocoa powder
- 4g (1 tsp) kosher salt
- 85g butter, melted
For the dark chocolate raspberry mousse (makes about 750g or 3 c):
- 7g (2 1/4 tsp) powdered gelatin
- 214g dark chocolate, chopped (I used half 54.5% Callebaut, half 70% Callebaut)
- 182g whole milk, divided
- 35g seedless raspberry puree
- 315g cream (35%)
For the dark chocolate mirror glaze (makes about 500g or 2 c):
- 60g cold water
- 12g (4 tsp) powdered gelatin
- 70g unsweetened cocoa powder (Dutch-processed)
- 140g heavy cream
- 75g room temperature water
- 200g granulated sugar
- Edible glitter paint
- Fresh raspberries
- Apricot jam
For the chocolate cake:
Preheat the oven to 350°F (175°C) with a rack in the middle. Grease an 8-inch round cake pan and line the bottom with parchment paper, then grease the pan again and dust with the cocoa powder.
In a small saucepan, melt the butter over low heat. When the butter has melted, remove from the heat, and whisk in the oil, milk, and vanilla. Allow to cool slightly while you prepare the rest of the ingredients.
Sift together the flour, cocoa powder, sugar, salt, and baking soda in a large bowl. Set aside.
Whisk the sour cream into the butter mixture, followed by the egg. Whisk the wet ingredients into the dry until combined. Add the hot coffee and whisk just until smooth.
Scrape the batter into the prepared pan and bake until a skewer inserted into the center comes out with just a few moist crumbs, about 25-32 minutes. Transfer to a wire rack to cool. Once the pan is cool enough to handle, run an offset spatula around the edge and turn the cake out to finish cooling completely. Wrap and chill the cake in the fridge until ready to assemble.
For the raspberry gelée:
Line a 6-inch cake pan with plastic wrap. Set aside.
Bloom the gelatin: Combine the cold water and gelatin in a small bowl. Stir with a spoon until the gelatin has dissolved. Allow to bloom for 5-10 minutes.
Cook the gelée: In a medium saucepan, bring the raspberry puree and sugar to a simmer over medium heat, whisking occasionally. Once the mixture comes to a simmer, remove from heat. Add the gelatin mixture and whisk to combine, making sure the gelatin completely dissolves.
Set the gelée: Pour the gelée into the prepared pan. Freeze until firm before adding crémeux, about 1 hour.
For the ruby raspberry crémeux:
Bloom the gelatin: Combine the gelatin and 15g of the heavy cream in a small bowl. Stir with a spoon until the gelatin has dissolved. Allow to bloom for 5-10 minutes.
Make the crémeux: Place the chopped ruby chocolate in a medium heat-safe bowl and set a fine-meshed sieve over it.
Place egg yolk in a medium bowl. Heat the corn syrup in the microwave until warm. Slowly whisk into the egg yolk until smooth (warming the corn syrup helps temper the yolk).
In a small saucepan, combine the remaining 125g heavy cream and whole milk. Bring to a simmer over medium heat.
Once the cream-milk mixture comes to a simmer, slowly whisk into the egg yolk mixture until well incorporated. Scrape the mixture back into the saucepan. Cook over medium heat, whisking constantly, until the mixture reaches 180F on a digital thermometer. Remove from heat, then add bloomed gelatin and whisk to combine thoroughly. Strain mixture over the chocolate. Let sit for one minute, then whisk together to form a smooth emulsion. Add the raspberry puree and whisk in thoroughly.
Freeze the crémeux: Pour crémeux over set raspberry gelée. Freeze uncovered until top is set, about 1 hour. Press a piece of plastic wrap on top and freeze until completely solid, at least 5 hours or overnight.
For the chocolate crumb:
Preheat the oven to 300F. Line a baking sheet with parchment paper or a silicone mat.
In a medium bowl, whisk together the flour, cornstarch, sugar, cocoa powder, and salt until well combined. Add the melted butter and stir until the mixture forms small clusters.
Spread the clusters in one layer on the prepared baking sheet. (I like to squeeze some clumps together to get a mixture of bigger and smaller pieces.) Bake for 20-22 minutes, stirring occasionally to promote even baking. The clumps should be slightly moist to the touch; they will harden as they cool.
Let crumbs cool completely, then transfer to an airtight container. Store at room temperature for up to a week, or in the freezer for up to a month.
For the dark chocolate raspberry mousse:
Note: prepare the mousse right before assembling the cake.
Combine the gelatin and 35g whole milk in a small bowl. Stir until the gelatin has dissolved. Set aside to bloom for 5-10 minutes.
Place the chopped dark chocolate in a medium bowl and set a fine-meshed sieve over it.
Put the remaining 147g milk in a small saucepan. Heat over medium heat until steaming, stirring occasionally. Once steaming, remove from heat and whisk in the bloomed gelatin mixture.
Strain over the chopped chocolate. Let mixture sit, without stirring, for 30 seconds; then whisk until the chocolate has melted and the mixture is smooth. Add the raspberry puree and whisk until completel.ombined. Let cool at room temperature while you whip the cream (you want the ganache to be slightly warm when combining with the cream).
Place the cold heavy cream in a large bowl (or in the bowl of a stand mixture fitted with the whisk attachment). Whisk on medium speed until soft peaks form.
Slowly pour the ganache into the whipped cream a little at a time, gently folding it in with a spatula until just combined. Transfer to a piping bag and use immediately.
Assemble the chocolate raspberry mousse cake:
Note: I recommend preparing the cake ring and trimming the layers before making the dark chocolate raspberry mousse.
Line the inside of a 6×3 cake ring with acetate and set on a plastic-lined sheet pan. Make sure you have space in your freezer where the sheet pan can fit flat so the cake can freeze properly.
Trim the cake and gelée-crémeux rounds so both are about 1/4″ to 1/2″ smaller than the cake ring (5 1/2″ to 5 3/4″ inches in diameter). Trim the cake to about 1/2″ thickness. (Save leftovers for snacking or another project, or see baker’s notes for thoughts on using more cake layers.)
Prepare the dark chocolate raspberry mousse (see above).
Pipe about 1/2″ of mousse into the bottom of the cake ring. Lightly tap the pan to ensure there are no air bubbles and smooth the top with an offset spatula. Set the cake layer on top of the mousse and gently press into the mousse until the mousse comes over the edge of the cake a bit. Pipe in about 3/4″ layer of mousse into the cake ring covering the cake layer. Set the gelée-crémeux layer on top of the mousse, gelée side on top. Gently press into the mousse until the mousse comes up the edge of the crémeux. Pipe mousse around the edge of the gelée-crémeux, then pipe in mousse to fill the remainder of the mold. Tap pan again to remove any air bubbles. Smooth the top so it is perfectly flush with the top of the mold. (You may have a little mousse leftover — consider it a baker’s treat!)
Transfer the sheet pan to the freezer. Freeze until solid, at least 3 hours or overnight.
Make the dark chocolate glaze:
Note: prepare glaze about 1-2 hours before you want to glaze the cake, or at least 3-4 hours before serving. After glazing the cake will still need fully defrost in the fridge before serving.
Combine the gelatin and 60g cold water in a medium bowl. Stir until the gelatin has dissolved. Set aside to bloom for 5-10 minutes.
Sift the cocoa powder into a medium saucepan. Add the 75g room temperature water and stir to form a thick paste. Add a small amount of cream and whisk to loosen. Add the remaining cream and sugar and whisk to combine.
Bring to a simmer over medium heat, whisking until the sugar has dissolved. Cook, whisking occasionally, until the glaze just comes to a boil, about 3-5 minutes.
Set a fine-meshed sieve over the bloomed gelatin and pour the glaze through the sieve. Whisk to combine and melt the gelatin. Blend with an immersion blender to remove lumps and air bubbles. Press a piece of plastic wrap against the surface and cool to 95F before glazing the cake (this took me about an hour). Right before glazing, strain glaze again into a tall pouring container to remove any air bubbles — pour from a low distance for best results. (Note: glaze can be stored in an airtight container for up to a week; rewarm in the microwave to 95F before using.)
Glaze the mousse cake:
At least 3 hours before serving, unmold and glaze the cake. Line a sheet pan with plastic wrap and set a sturdy plastic container or 4″ cake pan on top. (You want something smaller than the diameter of the cake so the glaze will drip off properly, but make sure it’s level and sturdy.) Take the cake out of the freezer and remove the cake ring. Move the cake to a 6″ cake board and remove the acetate. Double check the glaze is at working temperature — at 95F — before glazing. If not, wrap cake tightly in plastic and keep in freezer until ready to glaze — the cake must be frozen and not starting to melt when the glaze is applied.
In one swift and confident motion, pour most of the glaze over the center of the cake. If everything is at the proper temperature, the glaze should flow down and cling to the sides of the cake. If there are any spots that get missed, use an offset spatula to gently smear some extra glaze on. Let set for a couple of minutes, then use an offset spatula to cut off any stray drips at the base of the cake.
Finish and serve the mousse cake
Use a cake lifter or a couple of offset spatulas to move the glazed cake onto a serving plate. (The extra glaze can be refrigerated in an airtight container for up to a week or frozen; rewarm before using.) Decorate with chocolate crumbs at this point if desired (they will adhere better when the glaze is still a little sticky). Transfer cake to the refrigerator to thaw completely before serving (at least 2 hours, or up to a couple days). Decorate with edible glitter paint, and fresh raspberries (brushed with some warmed apricot jam for shine), if desired, before serving.