Nutella Cake

For the cake

1. Preheat the oven to 325 degrees F and prepare the baking strips by soaking them in water.
2. Spray three 8-inch round cake pans with cooking spray. Line the base of the pans with a circle of parchment paper and line the sides with a thin strip of parchment.
3. Combine the dry ingredients by sifting the flour, cocoa, baking soda, baking powder and salt into a large bowl then stir in the sugar.
4. In a separate bowl combine the wet ingredients. Whisk together the buttermilk, vegetable oil, Nutella, diluted coffee, eggs, and vanilla extract.
5. Gradually pour the wet mixture into the dry mixture while mixing continuously to prevent any lumps forming. The batter will be quite runny.
6. Pour the batter evenly between the three pans.
7. Bake the cakes for 60-70 minutes. Check the cakes after 60 minutes by inserting a toothpick into the center. If it comes out clean or with a few crumbs attached remove the cakes from the oven. If the batter is still wet, bake for a further 5-10 minutes before retesting.
8. Transfer the cakes to a cooling rack and remove the baking strips. Allow them to cool in the pans for 15minutes, then carefully invert them onto the cooling rack and remove the parchment paper.
9. Allow the cakes to cool completely before wrapping them in plastic wrap.
10. Set them aside to assemble the next day or if you are assembling the cake the same day, pop them into the freezer for 30 minutes before you prepare them for stacking.

For the Nutella ganache

1. Place the chopped chocolate into a large bowl.
2. Pour the cream into a small saucepan and stir over a medium heat. Heat until it reaches 185°F or until it starts to bubble around the edges.
3. Turn off the heat and pour the hot cream over the chocolate. Let it sit for 10 minutes to allow the cream to melt the chocolate. This step will also help to prevent the ganache becoming grainy.
4. To create a smooth ganache, start whisking the cream and chocolate together in the center of the bowl. Once the ganache starts to form, whisk in the remaining cream and chocolate from the sides of the bowl.
5. Add the Nutella and mix until smooth and shiny.
6. Set 1 1/2 cups aside for the frosting and pour the remainder into a heatproof bowl for the drip design on the cake. The ganache will thicken as it cools.

For the frosting

1. In a large mixing bowl, beat the butter until smooth.
2. Slowly mix in 1-2 cups of powdered sugar and the vanilla extract.
3. Add the remaining powdered sugar 1 cup at a time, mixing slowly until it is all combined. Beat faster for 2-3 minutes until it is light and fluffy.
4. Mix in the reserved 1 1/2 cups of the Nutella ganache until combined. If the ganache has become too firm, rewarm in short bursts in the microwave until it has softened.

For assembly

1. Use a large, serrated knife to trim off the tops of the cakes. Each layer should be approximately 1¼ inch thick.
2. On a cake turntable, secure an 8-inch cake board onto a 10-inch cake board with a little frosting.
3. Secure the first cake layer onto the board with a little more frosting.
4. Place a large round tip into a piping bag and half fill with the Nutella frosting. Pipe a layer of frosting onto the cake layer. Repeat this process with the second layer and top with the third layer.
5. Use a large, serrated knife to trim around the sides of the cake. Trim away any cake that overhangs the 8-inchboard to create flat sides. This will help to create a smooth covering of frosting.
6. Remove the offcuts and spread a thin layer of frosting all over the cake to create a crumb coat. Chill the cake in the refrigerator for 15 minutes until set.
7. Using an off-set spatula, liberally spread a thick layer of frosting over the cake. Scrape the top and around the sides with a tall cake scraper to create a smooth finish. You may need to apply a few coats to get a smooth finish. Freezing or chilling the cake for 10 minutes in between coats also helps to achieve a smooth finish.
8. To create a super smooth finish, heat the scraper in hot water and dry before sweeping it around the sides for a final time.
9. To firm up the frosting before adding the drip, chill the cake in the refrigerator for 30 minutes.

For the Nutella ganache drip

1. If the ganache has started to harden, rewarm it in short bursts in the microwave or over a pan of simmering water until it is the consistency of thick syrup.
2. To test the consistency, place a cake tin upside down onto the turntable.
3. Fill a piping bag a third full of the ganache and cut 3/16ths of an inch off the end.
4. Hold the piping bag above the edge of the cake tin and squeeze gently, then firmly in intervals to create different size drips down the side of the tin as you turn the turntable. If the drips stops a third to halfway down it is ready to use. If they run all the way down it is too runny so wait a few minutes before trying again. If it doesn't drip, then scrape the ganache out of the piping bag and warm again to make it runnier.
5. Swap out the cake tin for the cake and create random drips around the top edge of the cake.
6. Fill in the top with the remaining ganache, spreading it out with the off-set spatula.
7. Chill the cake for 15 minutesto set the top before piping the rosettes.

For the decorations

1. On a piece of parchment paper, draw around an 8-inch round board to create a circle and cut it out.
2. Fold the circle in half, then half again, then fold the quarter into three. Open it out, it should have 12 folds.
3. Place the circle on top of the cake and use a toothpick to mark the cake at each fold. These are your guide points for piping the rosettes.
4. Place a closed star tip into a piping bag and half fill the bag with the remaining frosting.
5. Pipe frosting rosettes onto the marked points on the cake.
6. Top each rosette with a Ferrero Rocher chocolate, then cut into slices and serve.