Flourless Hazelnut Dark Chocolate Truffle Cake Recipe

Do you love, LOVE, LOVE flourless chocolate cake as much as I do?  I was introduced to this uber-rich, chocolate truffle-like dessert when I spent a post-graduate year in France in 2005, and it changed my view of desserts forever more. I had never liked vanilla cake, nor did I like sponge cake or pound cake, even when they were called 'chocolate' simply because cocoa powder had been added to their recipe.  So when I had my first taste of flourless chocolate cake - made mostly with butter, real chocolate and eggs, I felt like it was the chocolate dessert that I had been waiting for my entire life. Why? Well, although it technically is a cake, it really is just a big slice of chocolate truffle on a plate.

And now I make flourless chocolate cake often.  Once you have the knowledge and the ingredients, it is actually quite simple to make. And I love to change up the ingredients of my flourless chocolate cakes to add just a little bit of a flavour twist.  My favourite is Raspberry Dark Chocolate, but I've even tried milk chocolate, white chocolate and a variety of fruit and nut flavours.

So today I thought I would share a festive holiday version that includes roasted hazelnuts and pure hazelnut butter.  This is a rich, savoury dark chocolate cake that is reminiscent of a large, bitter-sweet hazelnut chocolate truffle. Sweeten it up by topping it with a chopped hazelnut-milk chocolate bar and some hazelnut buttercream and you will have a luscious dessert.

Here is the recipe:

Flourless Hazelnut Dark Chocolate Truffle Cake

For the cake:

• 8 ounces / 227 grams of 70% dark chocolate (I used organic and Fair Trade Camino brand of chocolate couverture), chopped in 1 inch pieces.
• 1/2 lb butter / 250 grams (for a milk/dairy free version, use equivalent in Coconut Oil), chopped in cubes
• 1 cup sugar (I have now made this cake with regular granulated sugar, organic golden cane sugar and a lower glycemic version with coconut sugar - they all worked out great)
• 4 eggs, at room temperature (place in a bowl of warm water if cold)
• 1 cup pure hazelnut butter or paste (Cacao Barry's Pure Hazelnut Paste is fantastic, but there is likely a small jar of another brand at your grocery store that you can also use)
• 1 tsp sea salt

For the glaze:

• 6 ounces of semi-sweet dark chocolate (56% to 65%)
• 1/2 cup cream or 1/3 cup water
• 1 tablespoon corn syrup, honey or agave syrup

For the topping:

• Whole Hazelnuts - roasted, OR
• A 100 gram milk (or dark) chocolate with whole hazelnuts chocolate bar, chopped

Optional: Hazelnut Buttercream Icing

• 1/2 pound butter, softened
• 2 cups icing sugar, sifted
• 1/2 to 3/4 cup pure hazelnut butter (to taste)

Prepare your pan and the oven:

1. Prepare a 10" springform or regular baking pan with a piece of parchment paper and by greasing the paper and the sides of the pan with a tablespoon of softened butter (bake at 25 minutes). Alternately, you can prepare two 5" pans and make smaller cakes with 6 servings (bake at 17 minutes only).
2. Preheat your oven to 350 degrees F.

To make the cake:

1. Place the chopped butter and chocolate in a heat-proof bowl over a double boiler (a small pot with 1 inch of water in it at a low simmer) and stir constantly until melted. Remove from heat. You can use the stainless steel bowl from your stand mixer, if it does not have a thick-plated or rubber base.
2. Add the sugar and stir well.  Let rest five minutes.
3. Add all four eggs and mix with a hand mixer (or stand mixer) until well blended (do not over-beat, if it starts to get fluffy, stop mixing).
4. If it was refrigerated, warm your hazelnut butter in the microwave for about 25 or 30 seconds. Then pour into the chocolate-egg mixture and mix with your hand mixer or stand mixer until mixed in.
5. Toss in the salt and mix for about 10 seconds more with your hand mixer or with a spatula.
6. Pour the entire mixture into your 10" baking pan, or if using two 5" pans, pour half the mixture into each. Spread around gently and tap on counter to even the cake mixture in the pan.
7. Bake the 10" cake for 25 minutes in the centre of the oven, or 17 minutes for the small 5" cakes.  Turn off the oven when the time is up and gently pull out the oven rack and leave the door open for 5 minutes or more until cooled (this prevents the centre from falling too quickly, leaving the sides to crack).
8. Take out of the oven and let cool completely on a cooling rack. Once cooled, refrigerate it for at least a 1/2 hour to 1 hour.
9. Run a warm knife around the sides of the pan to ensure the cake does not stick. Remove the springform sides and flip upside down onto a serving plate (this is easier if you place your serving plate upside-down on top of the cake and flip over gently). Extract the parchment paper carefully, then decorate.

To make the glaze:

1. Place your chopped chocolate in a stainless steel, glass or plastic bowl.
2. In a small saucepan, bring the cream (or water, if using) just to a boil. 
3. Immediately pour the liquid over the chocolate and stir slowly with a wooden spoon until the chocolate is melted and well blended.
4. Add one tablespoon of corn syrup, honey or agave syrup to add a shine to the glaze.
5. Pour the glaze over the cake slowly and let it run to the sides. You can either let it drip lightly over the sides, or use a small offset spatula to smooth out the sides.  You will need a paper-towel to clean around the edges of your serving plate if it spreads.
6. Top with the chopped up hazelnut-chocolate bar or the roasted hazelnuts. Decorate with hazelnut buttercream, to add a little sweetness and more hazelnut flavour (see recipe below).

To make the Hazelnut Buttercream:

1. Beat the butter in a stand mixer bowl (or mixing bowl with a hand mixer) until softened and slightly fluffy. 
2. Add the icing sugar slowly while beating. Be sure to stir the bottom of the bowl with a spatula so no lumps form and beat again.
3. Add the hazelnut butter and beat. 
4. You can also add 1/4 cup cocoa powder for a chocolaty appearance and flavour or some melted milk or dark chocolate (not warmer than 82 to 86 degrees F).
5. Place in a decorator bag and decorate all around the top and sides of your cake, or spread in the middle and decorate however you wish! Just remember that this cake does not need a lot of buttercream, as it is already fairly rich in flavour and, well, butter.

Enjoy and indulge happily!