If you are a coffee fan, then this cake will be right up your street! Soft, moist and light sponge, flavoured with espresso coffee, sandwiched with silky-smooth mocha buttercream, topped with chocolate ganache and chopped walnuts.
How to make coffee cake from scratch
This coffee walnut cake requires just a little bit more of an effort, but it is totally worth it! The sponges are wonderfully moist, yet light and delicate, with that luscious, silky-smooth mocha buttercream in the middle. It will make a great centerpiece at your festive table, but is equally great as a Tuesday-after-dinner-treat.
To make sure it turns out just right, here are few tips to follow:
- Make sure your ingredients are at room temperature- It's really important that your eggs, butter, cream and sour cream are all at room temperature before starting. It will not only create a smooth batter, but will also allow your cake to bake evenly. Always take the ingredients out of the fridge for at least 30 minutes before baking.
- Wait for the coffee to cool- When mixing instant coffee and boiling water for the sponges, make sure you give it time to cool. You will be adding eggs to this mixture, so you don't want to end up with scrambled egg there!
- Toast the walnuts gently- Toasting the walnuts elevates their flavour and brings out even more of that delicious nutty flavour and texture. Easiest way to do it is by simply heating up a frying pan over a medium heat and adding the nuts. Toast them until they are fragrant and start going a bit darker in their appearance. Make sure to keep an eye on them, as they can burn quickly!
- Cake pans- Make sure you prepare the cake pans as per the instructions in the recipe. Grease them up lightly, then cover the bases of tins with baking paper. Finish off with dusting the cake tins with flour and tapping off any excess.
What can I use instead of sour cream?
The sour cream that this recipe calls for, is used here due to it's acidity. When it is combined with baking soda, the two work together to break down the gluten and create that light, yet moist texture.
If you don't have any sour cream on hand, you can substitute it with same amount of yogurt. Full-fat Greek yogurt will work best, but low-fat or even fat-free one can be used as well.
What is the best chocolate to use?
When it comes to chocolate in baking, I'm a strong advocate of using best you can afford. Dark chocolate is always my choice, because it just has much more flavour, without the added sweetness. It also helps to stabilise the bakes, because it has higher cocoa content, in comparison to sweeter, milk chocolate.
That being said, if you are not a fan of dark chocolate, this recipe will also work with milk chocolate. However, the appearance of the cake will be lighter, and the flavour will not be as intense.
What's the best way to add buttercream?
This is totally optional, but and extra step which is worth taking. When spreading the buttercream on top of one of your sponge cakes, you can do it two ways;
- Use a palette knife- Simply transfer the buttercream from your mixing bowl onto the cake, and use a palette knife to spread it in an equal layer.
- Transfer the buttercream into a piping bag- my proffered method. It's just easier to achieve that smooth, even top, when you simply pipe the buttercream in circles on top of the sponge cake.
How to store your cake
If you want to store this coffee cake, you can do so, at room temperature for up to 2 days. If you are keeping it for any longer than that, I would recommend to keep it in the fridge for up to 5 days.
The ganache and buttercream will become harder and much more solid after storing it in the fridge, so I would advise to take it out of the fridge and allow it to sit at room temperature for about 15 minutes, before serving.
Keeping it in a cake caddy or container will prevent your cake from drying out, so it's a good idea to invest in one.
As always, thanks for tuning in! If you try this, or any other of my recipes, I would love to hear from you! Leave me a comment or a rating below the recipe card, it always makes my day to hear from you guys!
Coffee walnut cake
- 2 x 20 cm round cake tins
- baking paper
- electric mixer
- mixing bowls
- food processor (optional)
For the sponges:
- 60 g unsalted butter melted and cooled
- 125 g plain flour plus extra for dusting
- 120 g dark chocolate chopped
- 2 Tbsp instant coffee or espresso powder
- 100 g walnuts toasted slightly
- 275 g light soft brown sugar
- ¾ tsp baking soda
- 2 large eggs eggs beaten
- 115 g soured cream full-fat greek yogurt will also work
- 2 tsp vanilla
- 50 ml olive oil
For the mocha buttercream:
- 1 Tbsp instant coffee or espresso powder
- 100 g unsalted butter room temperature
- 150 g icing sugar sieved
For the ganache:
- 75 ml double/ heavy cream
- ¾ Tbsp instant coffee/ espresso powder
- 3 Tbsp light brown soft sugar
- 50 g dark chocolate chopped
- 30 g walnuts toasted and chopped
To make sponges:
- Pre heat the oven to 180 C (160 C fan). Lightly brush the cake tins with some of the melted butter. Line the bottom of the cake tins with baking paper, then dust the tins lightly with flour, tapping out any excess. Place a heatproof bowl on top of a small saucepan with simmering water (making sure the bottom of the bowl doesn't touch the water). Add chopped dark chocolate to the bowl and allow it to melt, stirring every now and then. Set aside to cool.
- Bring a kettle to boil. Mix the instant coffee/ espresso powder with 250 ml of boiling water and set aside to cool. Using the food processor (or a knife), blitz (or chop) toasted walnuts until finely ground/ chopped.
- In a bowl of an electric mixer, mix together the ground walnuts, sugar, flour, and baking soda. Add a pinch of salt. In a medium jug, mix together cooled coffee, eggs, soured cream, vanilla, melted butter and olive oil. With your electric mixer running on low speed, gradually add the wet ingredients to dry ones. Combine until smooth, and add melted chocolate. Mix for further 10- 15 seconds. You should have thin, smooth batter at the end.
- Divide the cake batter between the cake tins and bake for about 35 minutes, or until toothpick inserted in the middle of each cake comes out clean. Leave the cakes to cool in the tins for about 10 minutes, before removing them from tins and transferring into a cooling rack to cool completely.
To make mocha buttercream:
- Dissolve the instant coffee/ espresso powder in 1 Tbsp of boiling water and set aside to cool. In a bowl of an electric mixer (you can also do this by hand), beat together the butter and sugar until smooth and fluffy, then gradually add the cooled coffee. Mix until combined, then top one of the sponges with this buttercream.
For the ganache topping:
- In a small saucepan over a medium heat, gently heat the cream, instant coffee/ espresso powder and sugar. Keep stirring the mixture often, to help the sugar and coffee dissolve. Take off the heat and add chopped chocolate. Stir this mixture until smooth and glossy, then set aside, allowing it to thicken and to cool down a bit.
- Gently place another sponge cake on top of the one topped with buttercream. Pour the chocolate ganache on top and add chopped and toasted walnut pieces. Enjoy!
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