Coffee & Walnut Cake with Coffee-Caramel Buttercream
The inspiration behind this classic cake (with a little twist) came from two separate events. The first was when I was asked to create a gluten-free cake incorporating coffee and walnut flavours for a special occasion taking place in June. The second was when my colleagues and I signed up for Race for Life taking place this July to raise money for Cancer Research UK, for which we need to start raising some money. So, I thought I'd better commence some recipe testing in preparation for the special occasion in June and some office bake sales! And a Coffee & Walnut Cake usually goes down a storm in my office...
So, here is the product of my first go at first recipe testing. Gluten-Free Coffee & Walnut Cake with Coffee-Caramel Buttercream. Overall, I'm pretty pleased with the cake, it's lightly infused with coffee and walnut flavour and the buttercream gives it a strong coffee kick with a sweet and creamy caramel finish. I'm slightly disappointed with the texture of the cake - it's a little dry - but I think I made the mistake of baking it a little too long. I've made adjustments in my recipe below to avoid this and plan to test out a couple other cake recipes to see if I can get a better result in the next few weeks. If I find something better I'll update my recipe accordingly!
Utensils: Medium heavy-based saucepan, whisk or spatula, cooking thermometer, 3 x 7 inch cake tins, non-stick baking paper, oil for greasing, cooling rack, electric stand mixer with whisk and paddle attachments, sieve, wire rack, cake turntable (optional), cake board / presentation plate, metal cake/dough scraper, piping bag, piping tip(s) of your choice.
Top Tip: I'll be completely honest, I had a slight breakdown on the journey to decorating this cake. It happened when I had successfully and lovingly prepared my Italian meringue buttercream on a Sunday afternoon but didn't have time to decorate the cake as soon as I had made it. "No problem", I thought. "I'll just pop the buttercream in the fridge and re-beat it tomorrow before decorating the cake".
In hindsight, what I should have done the next day was take the buttercream out of the fridge and allow it to come to room temperature before re-beating it (for the love of God, please do this if you want to avoid the below nightmare). Of course, impatient me did not do that. No, I just bunged it all in the mixer still cold from the fridge and set the beater going.
What I soon found out was that the buttercream separates when the butter is too cold. I ended up with quite an unpleasant mess of separated egg white and churned butter. At that point, I was very frustrated with myself. But, however bad your buttercream looks, there are ways to fix it. To fix my mess I took a few spoonfuls of the butter, microwaved it for about 10 seconds and then added it back to the buttercream while beating. I carried on doing this with the cold butter until the buttercream thankfully returned to the smooth, light and fluffy consistency that I had created the day before.
200g granulated sugar
90g unsalted butter, cut into small cubes and at room temperature
120ml double cream
Gluten-Free Coffee & Walnut Cake
225g unsalted butter, softened
225g caster sugar
4 large eggs, lightly beaten
2 heaped tablespoons fine ground coffee powder
225g gluten-free self-raising flour, sifted
75g chopped walnuts
Coffee-Caramel Italian Meringue Buttercream
400g unsalted butter, at room temperature (but not too soft)
6 large egg whites
1 teaspoon cream of tartar
225g caster sugar
1-2 tablespoons fine ground coffee powder (to taste)
3 heaped tablespoons caramel (or more to taste)
Makes: One 3-layer 7 inch cake
1. Make the caramel: First, prepare your ingredients. Spread the granulated sugar in an even layer over the bottom of a medium heavy-based saucepan. Weigh out the butter and cut into small cubes. Measure out the double cream. Set both to one side until needed.
2. Heat the sugar over medium-high heat, whisking or stirring gently with a spatula as it begins to melt. The sugar will begin to form clumps. Keep whisking and the lumps will melt back down. Once all the sugar has melted, stop whisking and swirl the pan gently as the sugar caramelises. Turn the heat down a little to stop the sugar from burning. Cook the sugar until it reaches a deep amber colour. It should look reddish-brown, and have a slight toasted aroma. If you have a cooking thermometer, the caramel should cook until it reaches around 175°C.
3. As soon as the caramel reaches this temperature, add the butter and stir. Be careful as the caramel will bubble up when the butter is added. Once the butter has melted, remove the pan from the heat and slowly pour the cream in. Stir until you have a smooth sauce. Set the sauce aside to cool for 10 minutes and then pour into a glass jar and let cool to room temperature. Once cool, place in the fridge to set until needed.
4. Make the coffee and walnut cake: Preheat oven to 180°C (fan 160°C). Grease and line 3 x 7 inch cake tins with baking paper. In an electric stand mixer with whisk attachment, cream the softened butter and sugar together until light and fluffy. Add the beaten eggs, a little at a time, with a tablespoon of flour to stop it curdling, and beat well between each addition of egg and flour. Add any remaining flour and mix well.
5. Mix the fine ground coffee powder with 1 tablespoon of hot water to form a smooth paste. Add to the cake mix alongside the chopped walnuts and stir to combine. Divide the cake mixture evenly between the three tins and bake in the centre of the oven for 15-20 minutes, until well risen and golden brown. Remove from the oven and allow to cool before turning the cakes out onto a wire rack.
6. Make the coffee-caramel buttercream: Cut the room temperature butter into cubes and place in the bowl of a stand mixer with paddle attachment. Cream the butter for a couple of minutes until smooth. Transfer to another bowl and set to one side. If your kitchen is very warm, place the butter in a cooler place until ready to use (the butter needs to stay at room temperature but not be too warm). Thoroughly wash and dry the bowl of your stand mixer, ensuring no grease remains, then place the egg whites in the bowl.
7. In a medium saucepan, add the sugar and water and bring to the boil over a medium heat. Boil until the syrup reaches 115°C (soft-ball stage) on a cooking thermometer. In the meantime, start beating the egg whites on low speed until foamy. Then add the cream of tartar and beat on medium-high speed until stiff peaks form.
8. With the mixer running, pour the boiling sugar syrup down the side of the bowl into the egg whites. Then turn the mixer on high speed and beat until the egg whites cool down to room temperature (around 10-15 minutes). Once at room temperature, turn the mixer down to medium speed and add the butter, one teaspoon at a time and keep beating until well incorporated. If the mixture looks curdled at any point, continue beating until smooth.
9. Mix the fine ground coffee powder with a little hot water to form a smooth paste. When the buttercream is nice and smooth, add the coffee paste and caramel and beat until combined. Feel free to vary the proportions of flavourings to suit your taste.
10. Assemble the cake: Trim the tops of each cake layer so that they are flat and so that the top crust of the layers are removed (place the trimmings in the fridge for late night snackies). Place the first layer on your cake board or presentation plate, securing with a little buttercream. Then spread an even layer of buttercream over the bottom layer. Place your second cake layer on top and repeat spreading another even layer of buttercream. Place the final cake layer on top.
11. Using the remaining buttercream, spread a layer of buttercream first around the sides of the cake and then the top. Use your cake/dough scrape to scrape some icing off around the sides to create a semi-naked effect. Smooth the top of the cake with a palette knife. Place the cake in the fridge for at least 30 minutes to chill before decorating the top of the cake with any remaining buttercream. For my decoration, I took inspiration from the wonderful Thida Bevington who makes coffee and walnut cake every week for a volunteer-run tea room! Check out her Instagram, there's lots of amazing decoration ideas for this cake on her page!
Storage: Store the cake in an airtight container in the fridge for up to 3 days. Allow to come to room temperature before serving. Any remaining caramel can be stored in a glass jar in the fridge for up to 1 month or in an airtight plastic container in the freezer for up to 3 months (defrost fully in the fridge before use). Any remaining buttercream can be stored in an airtight plastic container in the fridge for up to 1 week or in the freezer for up to 3 months (defrost in the fridge and then allow to come to room temperature before using).