Ingredients for the Chiffon base

7 eggs, large and at room temperature
325 g sugar (200g for the yolks and 125g for the white)
120 ml water
120 ml vegetable of hazelnut oil
1 tbsp baking powder
2 tsp vanilla extract
¼ tsp fine sea salt
125 g flour, cake & Pastry
100 g flour, all purpose
200 g whole hazelnuts
¼ tsp cream of tartar

Setting the cake pan & preparing the hazelnuts: 

1. Position a rack in the middle of the oven and preheat to 325°F

2. Prepare your cake pan (or cake ring) with a strip of parchment paper around the inside for easy removal of the cake when cooked. Do NOT grease the pan or the parchment paper!

3. Place the whole hazelnuts on a baking sheet and place into the oven to slightly toast and to dry their skin. After about 3 minutes, shake the tray and place back in the oven, repeating the shaking process approx. every 3 minutes until hazelnut are lightly browned and most of the skins are flaked off. (It may take up to 8-10 minutes. Do not overbrown the hazelnuts as they will get bitter).

4. When done, allow the hazelnuts to cool a bit, then rub them in your hands to flake off as much skin as possible (you can also spin and shake them using a salad spinner to get their skins off!)

5. Keep a few whole peeled hazelnuts for the cake décor and ground the remaining using a food processor. NOTE: Do not overground them as they will start to release their oil and will become pasty! IMPORTANT: Set aside about 50g of chopped hazelnut for the Chantilly.

Making the Chiffon cake base:

1. Separate the egg yolks from the egg white making sure there is no trace of yolk into the white. Set the egg white aside.

2. In a large bowl or in your stand mixer fitted with the whisk attachment, mix the egg yolks with 200g of the sugar and the water for about 1 minute until the mixture lightens slightly in color. Whisk in the oil, baking powder, vanilla, and salt. Remove and set aside.

3. In the meantime, sift the flours into a bowl over the ground hazelnuts (minus 50g of ground hazelnut that you kept for the Chantilly). Mix by hand until just combined. 

4. Fold the flour/nut mixture A LITTLE AT A TIME into the fluffy egg yolk mix until JUST INCORPORATED. Do not over mix.

5. In the bowl of your stand mixer fitted with the whisk attachment, whip the egg whites and cream of tartar on medium-low until the egg whites become frothy, about 2 minutes. Then, increase the speed to medium-high and keep whipping to soft peak, about 3 minutes. 

6. Turn down the mixer back to medium, then slowly add the remaining 125g of the sugar.Increase the speed to medium-high and continue whisking until stiff peaks form, about 2 minutes. If the meringue flop over the whisk, they need more time; if they hold a point, you’re set.

7. Gently fold a third of the whipped whites into the batter until just incorporated. Be sure to fold with the lightest touch, so as not to deflate them. Add another third and fold them in, followed by the final one, folding until just combined.

8. Transfer the batter to the pan, smooth the top with a small offset spatula if needed and bake for about an hour or until the top springs back when pressed with a fingertip and a bamboo skewer inserted in the middle comes out clean.

9. Remove from the oven gently run a long knife around the outside edge between the cake and the parchment paper and carefully lift or invert the cake on a baking rack. Allow to cool for about an hour or until it comes to room temperature.
   

Ingredients for the Nutella ganache

250 g Nutella
120 ml cream (33%)
2 tbsp vegetable oil or hazelnut oil

Making the Nutella ganache:

1. Place the Nutella in a small bowl. In a small saucepan over medium heat, warm the cream until tiny bubbles appear around the edges, about 3 to 5 minutes. IMPORTANT: Cream should NOT be too hot!

2. Pour the cream over Nutella and let it sit for about 1 minute. Using a fork, begin stirring from the center of the bowl until the cream and Nutella are thoroughly combined. Add the oil and continue to stir until just emulsified.

Ingredients for the Hazelnut Chantilly

250 ml cream (33%), cold
¼ cup icing sugar
50 gr ground hazelnut (from Chiffon base)

Making the Hazelnut Chantilly:

1. In the bowl of your stand mixer fitted with the whisk attachment, whip the cream on medium speed with the icing sugar to soft peak. Then add the ground hazelnut and mix for another 15-20 seconds or until medium/hard peak. Keep refrigerated until needed.

Assembling the cake

1.  Slice the Chiffon cake base into 3 even layers.

2. Place a quarter of the Nutella Ganache on the first layer, then place the second layer on top of the first one and add another ¼ of the ganache. Place the third layer over the second and add another ¼ of the ganache. Cover with the four (top) cake layer and, using an off-set spatula, evenly spread the remaining quarter of the ganache on the top of the cake.

3. Using the off-set spatula, spread some Hazelnut Chantilly around the outside of the cake for a smooth finish. Sprinkle a little chopped hazelnut on the top edge of the cake between the top ganache glaze and the Hazelnut Chantilly edge. Pipe a few “rosettes” of Chantilly on the top of the cake and garnish each one of them with the whole hazelnuts you would have saved aside (see preparing the hazelnuts – step 5)

4. Refrigerate the Nutella cake for at least one hour before serving.