Hazelnut Cake with Hazelnut Penuche

This might be one of the best cakes I’ve ever made. Hazelnut lovers, THIS IS FOR YOU. I don’t know which I like better: the cake or the frosting? I want both on everything. The nuttiness of the hazelnuts comes through very prominently, the texture of the cake is so so soft and moist, but it’s the flavor that really makes it stand out. Incomparable. 

Key Recipe Ingredients 

Hazelnuts: Blanched hazelnuts are really best for making hazelnut butter. If you absolutely can’t find them, use raw and unblanched but try to get the skin off right after toasting so you don’t have too many skin bits in the butter. 

Brown sugar: I used light brown sugar but dark should be fine too. Don’t substitute with turbinado (it’s not moist enough) or organic brown sugar (ditto). 

Cake Flour: Cake flour has a finer mill and added cornstarch which gives this cake its extra tender crumb. If you can’t find it, sub 1 tablespoon of the flour for 1 tablespoon of cornstarch or tapioca starch. 

Buttermilk: The tang and cream of buttermilk do wonderful things to make this cake have an incredibly tender crumb. You may sub with kefir (plain) or with a watered down yogurt. 

Salt & Vanilla: Fine sea salt (halve the amount if you are using table salt) and pure vanilla. 

Canola oil: any basic and flavorless oil will do. Have access to hazelnut oil? Use that! Otherwise I’d stick to something that won’t take away the flavor of the cake. 

Making hazelnut butter or hazelnut paste from scratch 

This is more time consuming (and slightly annoying) than hard. 

First you’ll toast the nuts – this brings out their flavor but also prepares them for grinding. 

Grinding the nuts into a paste takes patience and some fussing over the food processor; as the nuts grind they’ll start to release their oils. You’ll need to keep opening the food processor and scraping down the sides and packing it into the bottom to get them to grind evenly. 

Just keep doing this for 5-7 minutes, you’ll see it turn from bits of powdery nuts, then it will thicken into a chunk which is mostly ground nuts but has enough ‘paste’ to hold it together. 

But keep going! Once you see it starting to turn loose and liquid it’s getting close. Keep going and processing on high until it’s like a really thin, runny soup. The video below will show you the consistency needed. 

You can store this in the fridge, it’ll keep for a few weeks. 

How to make hazelnut cake using actual hazelnuts 

Baking this cake is a fairly simple process, it’s all in a bowl, just use a whisk or a hand mixer. 

Whisk the eggs and sugar: whisk until you have a very light, smooth texture. It’ll look like melted ice cream, thick and light, oozing off the spoon. 

Emulsify the oil then the nut butter: You’ll add the oil slowly, while mixing, so that it can emulsify into the sugar and eggs. Then do hazelnut butter the same way. 

Sift in the dry ingredients: Once it’s all sifted in, stir the batter and while you’re doing so pour in the buttermilk and stir until you have a very smooth but runny batter. Don’t worry about thickness, this looks like soup now but it’ll turn into a cake soon enough. 

Careful to whisk just the right amount and bake until the center springs back or a toothpick comes out clean.   

Penuche frosting “pen-oo-che” 

This is one of those cake toppings that is so basic and homey, it’ll remind you of your grandmas bakes from back in the day. The first time I came across it was  after I saw the deep caves on this banana cake. To me it’s a lot like making fudge: you cook butter and sugar together, then add milk and powdered sugar. 

While hot, the consistency is very loose, like a thick soup. As it cools though it settles into a firm but soft layer. The texture is somewhere between a glaze and a buttercream. 

I’m obsessed with turning penuche frostings nut- based, if you are a newsletter subscriber you’ve come across these banana cinnamon rolls with a peanut butter penuche, and I’m bound to have that pb penuche on some brownies or cake sometime before this year clocks out. 

Cooking penuche: It’s important not to over or under cook the sugar and butter, once the butter is melted, pour the sugar in and whisk. Then leave it to cook for exactly 2 minutes on medium heat. The brown sugar will have dissolved and it’ll look shiny. 

Whisking penuche: Make sure this is well sifted! This is going to be your excuse for skipping arm day at the gym. Getting that powdered sugar to dissolve fully into the hot base is going to take quite a bit of strength and vigorous whisking. Keep at it until it’s smooth!  

How to make hazelnut penuche frosting 

For this hazelnut based penuche frosting we’re going to make a basic brown sugar penuche: melt the butter then cook it with the sugar, once it’s boiled for a few minutes we’ll add milk. 

But before we move on to adding the powdered sugar, we’ll add some more of that wonderful hazelnut butter we made, stir well along with some salt and vanilla, then get vigorous and stir in the powdered sugar. 

I will say, penuche is SWEET. If you don’t have a sweet tooth you might not enjoy it as much. In this case I’d have the cake as is or top with a thin layer of glaze. 

Storing hazelnut cake 

This keeps great at room temperature. The edges where exposed will dry out a bit but I’d hesitate to keep it in an airtight container because the penuche might get overly soft and messy. 

Hazelnut Cake with Hazelnut Penuche

Supersoft and moist hazelnut butter cake made with freshly toasted and ground hazelnuts. This hazelnut cake is frosted with a hazelnut penuche frosting.

Prep Time: 30 minutes mins

Cook Time: 30 minutes mins

Yields: 1 8" square cake

5 from 4 votes

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Ingredients

Hazelnut Butter

• 2 cups hazelnuts

Hazelnut Cake

• 2 large eggs
• 200g or 1 cup brown sugar
• 1 ¼ tsp baking powder
• 75g ⅓ cup hazelnut butter
• 90g ½ cup canola oil
• 130g or 1 cup cake flour
• 110g or ½ cup buttermilk or plain kefir
• 2 teaspoons pure vanilla extract
• ½ tsp fine sea salt

Penuche Frosting

• 56g or ¼ cup butter
• 65g or ⅓ cup brown sugar
• 60g or ¼ cup whole milk
• 75g or ⅓ cup hazelnut butter
• 1 tsp pure vanilla extract
• ¼ tsp fine sea salt
• 175g or 1 ¾ cups powdered sugar sifted

Method

Make the hazelnut butter (it can be made ahead of time and stored in the fridge)

• Preheat the oven to 350 F. Set the hazelnuts on a cookie sheet and toast for 10 minutes, shaking the pan around 5 minutes for even heating.
• While still warm, put the hazelnuts in a food processor and begin grinding them. As needed, stop the machine and scrape down the ground nuts, keep going as you start to see a thick paste forming, then a looser paste, and after about 10 minutes or so, you’ll have a very loose soup like paste. Transfer to a mason jar.

Make the cake

• Preheat the oven to 350 F. Line a 8 or 9” square pan with parchment paper.
• Crack the eggs into a bowl (use a bowl and a hand mixer or a stand mixer) and add the sugar, immediately begin beating them (paddle attachment for a stand mixer) until it becomes very light and frothy. Add the oil while beating it and mix to combine.
• Add the hazelnut butter, vanilla and salt and beat to combine.
• Sift the cake flour over the batter, along with the baking powder. Turn the mixer on, and while it’s beating pour in the buttermilk. Mix until the cake batter is combined and shiny.
• Pour into the prepared pan. Bake the cake for 30-40 minutes, it’s done when a cake tester comes out clean or when you can press the top and it springs back.
• Let it cool before making the topping.

Make the penuche

• In a pot, add the butter and set over medium low heat. Once it’s melted, add the sugar and whisk to combine. Let it cook and come to a boil for about 2 minutes. Then add the milk and whisk. Cook the mixture for another 2 minutes without stirring, then remove from heat.
• Add the hazelnut butter, salt and vanilla and stir to combine. Add the powdered sugar and whisk, vigorously, to break up all the sugar bits until you have a very smooth, shiny frosting (it won’t be thick - don’t worry).
• Pour it over the cake in an even layer and leave it to set. Soon after you’ll notice the penuche has a matte top and is thickening. After about an hour (you can hasten this along if you set it in the fridge) it’ll set into a soft but stable layer.

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