This is the most delicious chocolate walnut cake - snack cake sized! It's covered in the dreamiest fudgy dark chocolate sour cream frosting and sprinkled with chopped walnuts. It only takes 15 minutes to prepare this cake, plus no mixer is required for the cake!
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This recipe was originally published in September 2021. It has since been updated with new images.
Sometimes you don't want a layer cake, as much as I love my chocolate orange layer cake, and want something simple like a snack cake! Using my favorite fudgy chocolate sour cream frosting (just like in Matilda's chocolate cake), this chocolate walnut cake is a chocolate lover's dream come true. If you want something even more chocolatey, you have to try my triple chocolate layer cake or my chocolate pistachio cake!
This is a really simple single-layer chocolate cake, so it's perfect to make when you don't have a ton of time. The cake layers are loaded up with finely chopped walnuts, and I added more walnuts on top of the frosting!
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Why you'll love this recipe!
- Oil Based Cake: This easy cake is based on my simple oil-based chocolate cake, no need to cream butter and no mixer required!
- Packed with Walnuts: Just before baking, the batter is folded with finely chopped walnuts.
- Fudgy Chocolate Frosting: This chocolate walnut cake is topped with a super fudgy dark chocolate sour cream buttercream, and then sprinkled with chopped walnuts. I love this buttercream because it isn't too sweet.
Recipe Testing
The base of this chocolate cake is my favorite! It's a dark chocolate cake that is super chocolatey thanks to hot coffee. The coffee isn't flavoring the cake, but it helps 'bloom' the cocoa powder, making the chocolate flavor richer. It's the same chocolate cake as my Matilda's chocolate cake and chocolate cake with chocolate cream cheese frosting, I just added finely chopped walnuts.
Ingredients Needed for Chocolate Walnut Cake
- Oil: Use a neutral oil in the cake, like canola, vegetable or sunflower oil. This will make the cake extra moist and no need to cream butter!
- Coffee: I add hot coffee to the cocoa powder which will bloom it, making the chocolate extra dark and chocolatey!
- Cocoa Powder: I'm using Dutch processed cocoa powder in both the cake and frosting.
- Buttermilk: Using buttermilk in the cake will make it super moist.
- Walnuts: you can swap out walnuts for pecans or hazelnuts. Make sure you chop them up very finely or they'll all sink to the bottom!
- Melted Dark Chocolate: try to use good quality chocolate for the frosting, it will make a huge difference!
- Sour Cream: I don't recommend substituting the sour cream for something else in the chocolate sour cream frosting.
See the recipe card for full information on ingredients and quantities.
Step by Step Instructions
Step One: Whisk together your sugar and egg for 1 minute until you have a few bubbles.
Step Two: Add the buttermilk, hot coffee, oil, vanilla extract and, salt and mix again.
Step Three: Add your cocoa powder and whisk until smooth. Add your flour, baking powder, baking soda and fold until there are no pockets of flour.
Step Four: Stir in the chopped walnuts.
Step Five: Pour into an 8x8 greased and parchment lined pan and bake for 35-45 minutes at 350 degrees Fahrenheit.
Step Six: Let the cake cool in the pan for about 10 minutes, then remove and let cool completely on a wire cooling rack.
Step Seven: Melt the chocolate in a small microwave safe bowl. I recommend doing it in 15 second increments, making sure you stir after every increment so it doesn't burn.
Step Eight: Beat your butter and confectioners' sugar together on low speed in your stand mixer or with a hand mixer until well combined. Turn the speed to high and mix for 2-3 minutes until fluffy.
Step Nine: Add in your cocoa powder and mix on low until the cocoa powder is combined - this stops it from flying everywhere! Increase the speed to medium and mix for 1-2 minutes. Pour in your sour cream, melted chocolate and salt and mix once more.
Step Ten: Spread the chocolate frosting on top of your cooled cake and enjoy!
Expert Tips & Tricks
- Kitchen Scale: I highly recommend using a weighing scale and measuring out your ingredients the metric way. It makes a huge difference to your baking and is the most accurate way to bake!
- Room Temperature: I make sure that all of my ingredients are at room temperature before I start the recipe, so pull out all of the ingredients (including the buttermilk!) before you start baking.
- Walnuts: Make sure your walnuts are finely chopped, I use my food processor to do this but you could also place them in a large ziplock bag and crush them with a rolling pin. If the walnuts are too large, they might sink in the chocolate walnut cake.
Recipe FAQs
Yes! So you can substitute the buttermilk for sour cream or full fat yoghurt, or you could make your own buttermilk. For every cup of milk, add 1 tablespoon of vinegar or lemon juice. Mix, then let sit for 5 minutes before using.
You can! Make it in a 9-inch round pan and bake for the same amount of time.
Keep it tightly wrapped and in the fridge for up to 5 days. When ready to eat, let it sit at room temperature so the frosting can soften, as it does harden in the fridge.
Try these chocolate recipes next!
Made This Recipe?
Make sure to leave a ⭐️ rating and review below! You can tag me on Instagram @alpineella or follow along on Pinterest, Facebook and TikTok!
Thank you!
Ella
Recipe
Chocolate Walnut Cake
Equipment
- 8x8 inch cake pan
Ingredients
Walnut Chocolate Cake
- 175 grams (1 cup) granulated sugar
- 1 egg room temperature
- 120 ml (½ cup) hot coffee
- 120 ml (½ cup) buttermilk room temperature
- 60 ml (¼ cups) vegetable oil
- ¼ teaspoon vanilla extract
- ½ teaspoon kosher salt
- 32 grams (⅓ cups) cocoa powder dutch processed
- 110 grams (1 cup) all purpose flour
- 1 teaspoon baking soda
- ½ teaspoon baking powder
- 64 grams (½ cup) walnuts finely chopped
Chocolate Frosting
- 85 grams (3 oz) dark chocolate chopped
- 110 grams (½ cup) unsalted butter room temperature
- 113 grams (1 cup) confectioners' sugar
- 42 grams (½ cup) cocoa powder dutch processed
- pinch kosher salt
- 60 ml (¼ cups) sour cream room temperature
Instructions
Make Cake
- Preheat your oven to 350°F/175°C. Butter or grease an 8 inch square baking pan and line it with parchment paper.
- In a large bowl, whisk together the sugar and egg for 1 minute.175 grams (1 cup) granulated sugar, 1 egg
- Add the buttermilk, hot coffee, oil, vanilla and salt. Whisk until it is smooth. Add your cocoa powder and whisk again until smooth120 ml (½ cup) hot coffee, ¼ teaspoon vanilla extract, ½ teaspoon kosher salt, 120 ml (½ cup) buttermilk, 60 ml (¼ cups) vegetable oil, 32 grams (⅓ cups) cocoa powder
- Add the flour, baking powder, and baking soda and whisk until smooth. Fold in your chopped walnuts110 grams (1 cup) all purpose flour, 1 teaspoon baking soda, ½ teaspoon baking powder, 64 grams (½ cup) walnuts
- Pour into your pan and tap on the counter to get rid of any bubbles. Bake for 35-45 minutes. A toothpick inserted should come out clean. Allow it to cool for 20 minutes in the pan, then lift it out and let it cool completely on a cooling rack.
Make Frosting
- Melt your chocolate in a microwave, stirring every 10 seconds so it doesn't burn.85 grams (3 oz) dark chocolate
- In your stand mixer with the paddle attachment, beat the butter and confectioners' sugar on low speed until well combined110 grams (½ cup) unsalted butter, 113 grams (1 cup) confectioners' sugar
- Turn the speed to high for 2-3 minutes until light and fluffy.
- Add in your cocoa powder and beat on low, then increase the speed to medium for 1-2 minutes.42 grams (½ cup) cocoa powder
- Add your sour cream, melted chocolate and salt and mix once more.pinch kosher salt, 60 ml (¼ cups) sour cream
- Spread over your cooled cake and decorate with walnuts.
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Taito says
Hi, i like my cakes not very sweet, do you think i can reduce the sugar? if yes, by how much could i till it had a negative effect on the batter?
thanks.
Ella says
Hi Taito! I haven't tested this with reducing the sugar, but I think you could reduce the sugar by 10% and not have it impact the structure of the cake! So remove 5 teaspoons from the cup of sugar. Because of the cocoa powder, if you do more than that it might make the cake bitter.
Margaret McCormick says
I’m a controlled diabetic. I converted this easily and it worked out well. Swerve and stevia for the sugar and the flour was half all purpose and half carbquick. The chocolate chips were Lilys dk and milk mixed. The texture was cake-like and not dense and heavy.. it worked good. I baked in a tube pan and the bake time was less than above. Thank you for this great recipe.
Kris says
I baked this for my birthday and it is hands down the best cake I've ever made! It was a huge hit! My mother said it's the best cake she's ever had. I am in the US and can confirm that the US measures are correct. Absolutely phenomenal chocolate walnut cake!
Ella says
Thank you so much for your review Kris, I hope you had a great birthday!
Susan says
Can this be made without nuts?
Ella says
Yes you can! Just follow the same recipe + directions but don't add the walnuts.
Alison says
Ohhhh so decadent and delicious!!
Ella says
thank you!!
Merlyn dsouza says
Hey!
Is it possible to substitute sour cream in this recipe ?
Thanks in advance !
Ella says
Hi there! Yup, if you check the notes in the recipe card I have a few substitutions for buttermilk and you can use sour cream!:)
Kelley says
May taste ok, but this recipe is organized so poorly it’s nearly impossible to follow. I must have scrolled 50+ times just to keep track of the mixing instruction and ingredients.
Nancy says
I agree. I just rearranged the ingredients in order of use when recopying. Have to do that for lots of recipes.
November says
I am scaling up this recipe by four, would you recommend doing the same with baking soda and powder (using 4 teaspoons soda and two teaspoons powder)?
Ella says
Hi! I haven't tested that but it should work!
Sharon says
I made this recipe (cake only) on New Year's Day and it turned out to be a hit. I used a cream cheese and whipped cream icing as I prefer the taste over buttercream. Thank you Ella. This one's a keeper for certain.
Ella says
Thanks so much for your review, so glad you liked it! The icing you used sounds delicious!
Judy Kahn says
Your cake looks divine. For the dark chocolate, what percent chocolate do you recommend? Thanks!
Ella says
Thank you! I usually use the Lindt 51% baking chocolate!
jon says
looks great! I would replace the vegetable oil with ghee for buttery upgrade that works great with cake
Ella says
I've never tried it with ghee, need to give that a try!
Natalie says
THIS WAS FANTASTIC!! Kids to adults went nuts over this especially the frosting. In my humble opinion, the cake gets better as it sits so next time I’ll make the cake the day before and frost right before serving!
Ella says
Thank you so much Natalie for this review!
Nicola says
Excellent recipe. So easy to make.