Chocolate Hazelnut Cake
If ever there were a cake to knock the socks off you chocolate lovers, this is it. Picture a light chocolate sponge cake, with a luscious mousse and chopped hazelnut filling, smothered in a decadent chocolate ganache. We first tried it at Bàcaro, our favorite restaurant in the Cayman Islands where we spend a week each winter. After enjoying it twice in one week, I asked for the recipe and Head Chef Federico Destro generously gave it to me. It was written in metric measurements, but I’ve converted them into the cups more familiar to Americans. However, if you buy a kitchen scale, I recommend using the metric system measurements, since baking by weight is always more accurate than using cups.
Federico’s recipe says it makes 30 portions, but the portions at Bàcaro are much smaller than what I served at my recent dinner party. I cut mine into 24 portions, still a huge amount for most home cooks, but I froze half of the cake for later gratification. It freezes perfectly with the chocolate mousse inside, but wait until the day you serve it to pour on the ganache, otherwise you risk losing that lovely sheen and soft texture.
Make sure you sift the dry ingredients and have the eggs at room temperature before beating them with the sugar. Beat for the required 10 minutes to give them the volume necessary for the cake to rise, since it contains no other leavening.
Pour into a pan that’s been buttered and floured. I also lined the bottom with a piece of buttered parchment paper to help release the cake without sticking.
When it cooled, I cut the cake in half down the middle since half serves 12 people, and cutting it in half then makes it easier to cut it into horizontal layers. You’ll spread the mousse between the two layers.
In my experience, the mousse is the hardest part to make, since it uses Nutella, which is stiff and difficult to incorporate smoothly with the melted chocolate, egg whites and whipped cream.
Blend in just about a third of the egg whites with the melted chocolate and Nutella to get the mixture a little lighter. Keep whisking until it starts to loosen a bit.
Add another third of the egg whites after the initial egg whites have been whisked in. It will still be stiff, but a little easier to whisk.
By the time you add the last third of the egg whites and the whipped cream, it will become much lighter in color and texture.
Spread the mousse over the bottom layer of the cake and sprinkle with chopped hazelnuts.
Place the top layer of cake over the mousse, then drizzle some of the diluted espresso coffee over the cake. As you can see, I lined each section of the cake in the pan with plastic wrap, to make it easier to remove one section and leave the rest in the freezer. Place the cake in the freezer for at least 4-6 hours.
After removal from the freezer, carefully cut into 12 sections.
This is the messy part — pouring the ganache on top. The recipe below includes more of the ganache than Chef Destro recommended, partly due to the fact that I’m not a chocolatier and wasted a good bit of chocolate, and partly due to the fact that I’ll take any occasion to eat more dark chocolate!
Here’s the way it’s served at Bàcaro, and you can see how much smoother the outer coating is, when a real professional is pouring the chocolate!
Still, there were no complaints about my version either. Place the cakes in the refrigerator, but set aside about 1/4 cup of the ganache and refrigerate it too. When it starts to harden just ever so slightly, scoop a little out with a demitasse spoon to make a chocolate ball on top, and place a hazelnut on top of the chocolate. I also added a small sliver of gold leaf — totally optional, but don’t forget the whipped cream!
The recipe may seem daunting, but you can make it the day before a dinner party or event, and keep it refrigerated. One caveat though – they look really tempting to husbands grazing for a midday treat. You’ve been warned.
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- FOR THE SPONGE CAKE:
- 10 eggs
- 2 cups (300g) sugar
- ¾ cup (50g) cocoa powder
- ¾ cup (50g) corn starch
- ½ cup (50g) all-purpose flour
- Pinch of salt
- 1 cup hazelnuts (150 g)
- 1 cup diluted espresso (250 ml)
- FOR THE MOUSSE:
- about 1⅓ cup (300g) dark chocolate
- 1 13 ounce jar (300g) Nutella
- 1¾ cup (400g) heavy cream (whipped to medium hard peaks)
- 4 tbsp sugar
- 4 tbsp rum
- 4 eggs
- FOR THE GANACHE (This is enough for half the cakes, since I froze half the cakes unfrosted. Just double if frosting the entire cake).
- 2 cups (about 425 grams) heavy cream
- 12 oz. chocolate (I used three, 4 oz. bars of Hershey's Special Darrk)
- TO MAKE THE SPONGE CAKE:
- Whisk the eggs and sugar at high speed for about 10 minutes.
- Sieve the cocoa powder, flour and corn starch and add them to the egg mixture gradually and folding slowly.
- Pour the mass into a half-size hotel pan (my pan measured 15" by 10" x 2.5" but the chef used a pan that was 20" x 10" x 2.5")
- Bake at 350F for 30-40 minutes or until cake pulls away from sides of pan.
- Let cool at room temperature, then wrap with plastic film and store in the fridge or freezer until needed.
- Cut the cake in half to make for easier handling, then cut each half in half horizontally, in order to have two layers.
- Then put some plastic wrap on the bottom and sides of the pan where you baked the cake, and put the layers inside, with separate pieces of plastic wrap for each half of the cake.
- That way, you can easily remove only half the cake and leave the rest frozen for later use.
- Each half of the cake made 12 servings, (30 for Chef Destro who cuts smaller portions) so unless you have a crowd of 24, you can keep half frozen.
- TO MAKE THE MOUSSE:
- Separate the egg whites from the yolks and set aside.
- Whisk the yolks with sugar and rum.
- Add the chocolate (previously melted) folding it slowly, then add the Nutella and combine (This is the hardest part because the Nutella is quite stiff. But keep at it.)
- Whisk the egg whites to hard peak, then gradually fold them into the chocolate mixture (again it's hard because the Nutella is so stiff, but once you have all the egg whites added, it loosens up and when you add the whipped cream, it will be just right consistency.)
- Fold in the whipped cream and set in the fridge until ready to use.
- TO ASSEMBLE THE CAKE AND FILLING:
- Leave the cake in the pan and remove the top layer.
- On the bottom layer of the sponge cake, drizzle with half the espresso.
- Set half the mousse on top of it and sprinkle with the hazelnuts.
- Place the top layer over the mousse and drizzle with the other half of the espresso.
- Cover and chill in the freezer for at least 4-6 hours.
- FOR THE GANACHE:
- Heat the cream, turn off the heat and add the chocolate, stirring to combine until smooth.
- TO FINISH THE CAKE WITH THE GANACHE:
- Cut the frozen cake in 24 portions, if you plan to serve all at one time.
- In that case, double the ingredients for the ganache.
- Otherwise, place half the cake in the freezer and cut the other half into 12 portions.
- Place them on a perforated rack and quickly coat them with the warm ganache.
- Place back in the freezer to harden.
- Repeat the coating process once more and place in the fridge until ready to serve.
- Save a bit of the ganache to use as a center dollop with a hazelnut perched on it.
- If you have any gold leaf, add a small piece to the top.