Toasted Hazelnut Chocolate Sheet Cake with Nutella Frosting

Rich fudgy chocolate cake and the creamy, nutty flavors toasted hazelnuts comes together in the ultimate dessert: Toasted Hazelnut Chocolate Sheet Cake with Nutella Frosting! This simple, but wow-worthy, sheet cake features finely ground toasted hazelnuts in the cake batter, which pairs beautifully with the deep, rich cocoa notes in the cake. The final Toasted Hazelnut Chocolate Sheet Cake is moist, fudgy, and toasty in flavor! The cake is finished with a generous smearing of a creamy Nutella frosting, making it perfect for young and old alike!

Making the Toasted Hazelnut ‘Flour’

The first step in making this Toasted Hazelnut Chocolate Sheet Cake is making the hazelnut ‘flour’, which is essentially just ground up toasted hazelnuts. Start by placing the hazelnuts onto a baking sheet and placing them into the oven for around 15 minutes. When ready, the hazelnuts should be slightly dark in color and the skins should look slightly blistered. Immediately transfer the toasted hazelnuts into a tightly wrapped kitchen towel. Allow the hazelnuts to sit in the kitchen towel and steam for 1-2 minutes. This ‘steaming’ will help loosen the skins. Next, using the kitchen towel, rub the hazelnuts together roughly to remove the skins (if a few are stuck onto some hazelnuts, that is fine!).

Allow the peeled hazelnuts to come to room temperature and then transfer them into a food processor with 1/2 cup of flour. Grind the nuts/flour until the texture becomes fine (a few medium pieces here and there is okay), ensuring you don’t over-process, as it will turn into a paste if you do.

How to make the Toasted Hazelnut Chocolate Sheet Cake

1. Prepare the hazelnut ‘flour’: As per the instructions above, toast the hazelnuts, peel them, then grind them with some flour in a food processor until they resemble almond flour. Set aside.

2. Combine wet ingredients: Add the eggs, sugar, vanilla, almond/hazelnut extract, sour cream, and oil, to a large mixing bowl, then beat together with a whisk until the mixture is smooth and well-combined.

3. Whisk together the dry ingredients: In a separate mixing bowl, add the remaining flour, toasted hazelnut flour, baking powder, baking soda, and salt.

4. Bloom the cocoa: Add the sifted cocoa powder to the warm coffee. Mix until smooth, and then add to the wet mixture from above.

5. Add the dry & wet together: Pour the wet mixture into the dry mixture, and whisk together until smooth. Try not to over mix though!

6. Add to pan & bake: Pour the Toasted Hazelnut Chocolate Sheet Cake batter into a 9×13” cake pan, then place into the oven to bake! When done, allow the cake to cool completely before frosting!

Why do you have to ‘bloom’ cocoa?

You’ll notice in the recipe instructions that you have to add the cocoa powder to hot coffee before adding it to the batter. This is known as ‘blooming’ that cocoa. The reasoning behind this process is that the hot liquid dissolves flavor particles within the cocoa powder, making the final product taste more chocolatey! While we’re at it, you may also be wondering why this Toasted Hazelnut Chocolate Sheet Cake, as well as many other chocolate cake recipes, call for coffee. Again, the reasoning for this is because the coffee actually intensifies that chocolate flavor! Neat, huh?!

What is Dutch Processed Cocoa?

This Toasted Hazelnut Chocolate Sheet Cake recipe calls for Dutch processed cocoa as the cocoa powder. ‘What the heck is Dutch processed cocoa powder’, you ask? Dutch processed cocoa is created by alkalizing regular cocoa powder to bring it up to a pH of 7. This process sort of strips the acidic properties out of the cocoa powder, leaving it with a much more mild, less astringent taste. By removing the astringency, the flavor of chocolate is able to shine through more, creating the illusion that it tastes more chocolatey! Definitely what we want for a chocolate cake recipe!

Be warned, however, that regular cocoa powder and dutch-processed cocoa powder cannot always be used interchangeably. Recipes that include baking soda need an acid to activate the baking soda to induce rising. In many recipes this ingredient is cocoa powder (pH=5.3). Therefore, using Dutch processed cocoa powder, which has a neutral pH, wouldn’t activate the baking soda, and another acidic ingredient would be required. For example, in this Toasted Hazelnut Chocolate Sheet Cake, that other acidic ingredient is sour cream (pH=4.5).

Get the Recipe: Toasted Hazelnut Chocolate Sheet Cake

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Fudgy chocolate cake and the creamy nutty flavor of toasted hazelnuts come together in the ultimate cake: Toasted Hazelnut Chocolate Cake & Nutella Frosting

Prep Time: 20 minutes mins

Cook Time: 35 minutes mins

Total Time: 55 minutes mins

Servings: 12 servings

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Ingredients

 

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Toasted Hazelnut Chocolate Cake

• 100 g Raw Hazelnuts
• 2 cups (240g) All Purpose Flour,, divided, measured correctly†
• 1 tsp Baking Soda
• 1 tsp Baking Powder
• 1/2 tsp Salt
• 2 Eggs
• 2 cups Sugar
• 1 cup Sour Cream
• 1/2 cup Vegetable Oil
• 2 tsp Vanilla
• 1/4 tsp Hazelnut or Almond Extract, (optional)
• 3/4 cup Dutch Processed Cocoa Powder, (regular cocoa can be used too)
• 3/4 cup Hot Freshly Brewed Coffee

Nutella Frosting

• 1/2 cup Unsalted Butter,, at room temperature
• 1/2 cup Nutella
• 1 1/2 cups Confectioners Sugar
• 1/4 cup Dutch Processed Cocoa Powder,, sifted
• 1 tbsp Heavy Cream

Equipment

• Food Processor
• Stand mixer

Instructions

 

Toasted Hazelnut Chocolate Cake

• Preheat oven to 350°F. Add hazelnuts to a pan and place into the oven to toast for 12-15 minutes. When done, immediately transfer into a kitchen towel, and wrap tightly. Allow the hazelnuts to ‘steam’ for 1-2 minutes. Next, using the kitchen towel, roughly rub the hazelnuts together to get the skin off (if a few pieces of skin remain that’s okay!). Allow the hazelnuts to cool to room temperature.
• Add the hazelnuts and 1/2 cup of the flour to a food processor. Grind until the hazelnuts are finely ground and resemble almond meal (a few larger pieces here and there are okay). Ensure you do not over-process (over-processing will turn the hazelnuts into a paste).
• Prepare a 9×13” cake pan with oil and parchment. In a large mixing bowl, add the flour/hazelnut mixture, remaining flour, baking soda, baking powder, and salt. Whisk together to combine. Set aside.
• In another large bowl, add eggs, sugar, sour cream, vegetable oil, vanilla, and hazelnut/almond extract. Whisk together until smooth and well combined.
• In a small mixing bowl or 2-cup liquid measuring cup, add the hot coffee and cocoa powder. Whisk together until well-combined and smooth. Allow to sit for 2 minutes, then add the cocoa mixture into the mixing bowl with the wet ingredients (eggs, sour cream, etc.), then mix until smooth.
• Add the wet ingredients into the bowl with the dry ingredients, and mix until smooth. Pour the cake batter into the prepared cake pan and place into the oven to bake (350°F) for 35 minutes, or until an inserted toothpick comes out clean. Allow to cool completely before frosting.

Nutella Frosting

• Add butter to a stand mixer fitted with the whisk attachment. Beat on high until butter is doubled in volume, and looks light and fluffy, about 3-5 minutes. Then add the Nutella and beat until well-combined with the butter.
• Turn the stand mixer to low and slowly add the confectioners sugar and cocoa powder. Beat on medium until completely incorporated and smooth.
• Add in the heavy cream. Beat until well-combined and fully incorporated.

Notes

† to measure flour correctly, use a spoon to scoop the flour into the measuring cup, then level off with a straight edge. Do not pack the flour into the cup, or scoop with the measuring cup straight from the bag/container. Alternatively, weigh the flour (1 cup = 120g or 4oz)

Cuisine: American

Course: Baking

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