This easy Coffee Walnut Sheet Cake is made in a traybake tin using a normal butter sponge cake recipe. Rich coffee and chopped walnuts lend a sophisticated flavour to this traditional British dessert. Then it is topped with a coffee flavoured icing and decorated with more chopped walnuts, making this the perfect sweet for your morning break.
This easy coffee walnut cake is perfect for everyday baking. It will give you 18 good slices and is ideal for a packed lunch when you fancy something sweet for your morning break with a cup of coffee.
Because it is baked in a traybake (Americans call it a sheet cake) tin, there’s no fussy layering involved. Simply bake one giant butter cake layer, slather it with delicious homemade coffee frosting and top with crunchy walnuts. It is delectable and easy.
The list of ingredients is short and includes mostly basic store cupboard staples, plus the decadent addition of walnuts.
A few notes about ingredients.
- I always use medium eggs at room temperature, unless otherwise stated.
- Do yourself a favour and use real butter rather than margarine. It has a much better flavour and contains more fat and less water than margarine, yielding a softer crumb. Butter cake even sounds better than margarine cake, right?
- The butter should be at room temperature, soft enough to easily indent with your finger, but not so warm as to be greasy.
- While the recipe calls for instant coffee powder, you can substitute regular coffee granules. Just note that you should crush them to a fine powder before use for better distribution.
- Buy the freshest walnuts that you can in small quantities to avoid them turning rancid. I buy mine from Nova Bakehouse at the Leeds Dock in Leeds. They offer a variety called Parisienne that is grown in France.
- TIP: Storing nuts in an airtight container will prolong their shelf life. If you have space, it is preferable to keep nuts in the refrigerator or freezer for storage.
- I love using brown sugars in cake baking. They add a slightly nutty, caramel flavour. If you only have white caster sugar or granulated sugar, that will be fine. You may need to beat the granulated sugar, which has a larger crystal, a little longer to get a fluffy result.
- TIP: You can make your own brown sugar by mixing 1 Tablespoon treacle with 200g white sugar.
- TIP: Keep your brown sugar soft by storing it in an airtight container with a piece of bread.
- For this cake, I used Self Raising Flour which includes a raising agent. TIP: You can make your own self raising flour by adding 1 1/2 tsp baking powder and 1/4 tsp salt to every 120g plain flour.
- For my American readers, please note that icing sugar and confectioners sugar are one and the same.
How to make a butter based sponge cake.
When baking, always preheat your oven. I also suggest you invest in an oven thermometer. It’s amazing how much difference the temperature can be in individual ovens. Using the appropriate temperature can make the difference between a perfectly baked cake vs an over-baked or under-baked one.
Grease and line the base of a shallow 29cm x 19 cm oblong tin (or 9x13in). It should be at least 2cm (1inch) deep.
Using an electric mixer, beat together the butter and sugar until light and fluffy. Do not skimp on this step! In order to achieve a nice crumb in a butter based cake, you need to create air pockets by whipping the sugar into the butter.
Add the eggs one at a time, adding a little flour in between each one. This will help prevent too much curdling. Mix until well combined. Add vanilla extract.
Add the remaining flour and instant coffee powder, mixing until just combined. Stir in chopped walnuts.
Pour the cake mixture evenly into the prepared tin. Bake for 20-25 mins or until baked through. Test the centre of the cake in different areas with a skewer until it comes out clean.
Leave in the tin to cool for about 10 mins, before turning out onto a wire rack to cool completely. Or you can leave it in the tin to cool before adding the coffee icing.
How to make Coffee Icing
Mix the icing sugar and instant coffee powder together. Beginning with 1 tablespoon of preboiled hot water. Start to mix the icing sugar and coffee powder until you have a thick spreading consistency, adding more water as needed. Go slowly and only add a little at a time. If it becomes too runny, just add more icing sugar.
When your cake has cooled completely, spread the coffee icing evenly over your cake. Before the icing sets, decorate with a scattering of walnuts. You may need to press them down a little if your icing has begun to set.
This coffee walnut cake will keep in an airtight container for a couple of days, but I doubt it will last you that long.
Need more recipe inspiration?
Sheet cakes and Traybakes are ideal for charity and bake sales.
Love coffee? You may also like to try these other coffee flavoured bakes.
Keen to Bake More?
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If you make this recipe, please leave a comment with a rating, to let me know how you got on.
Easy Coffee Walnut Cake
- Tray bake or sheet cake tin 29cm x 19cm x 2cm
Ingredients – Imperial /oz are approx weights which are calculated by a 3rd party app
For the cake
- 3 level tablespoons of instant coffee powder This gives the cake a strong coffee taste. Use 2 tablespoons for a milder coffee flavour.
- 200 g butter softened
- 200 g soft light brown sugar
- 4 medium eggs
- 200 g self raising flour
- ½ teaspoon vanilla extract
- 50 g walnuts roughly chopped
For the Coffee Icing Topping
- 150 g icing sugar sieved
- 1 tablespoon instant Coffee Powder
- 1 tablespoon + more pre boiled Hot water
- 50 grams walnuts roughly chopped
Make the cake
- Preheat the oven to 180deg conventional or 160deg fan assisted. Grease and line the base of a shallow 29cm x 19 cm oblong tin or similar. At least 2cm/1inch deep.
- Using an electric mixer, beat together the butter and sugar until light and fluffy.
- Gradually add the eggs one at a time. Adding a little flour in between each one. This will help prevent too much curdling.
- Mix until well combined.
- Add the remaining flour, instant coffee powder, chopped walnuts and vanilla extract. Mix together until well combined.
- Pour the cake mixture evenly into the prepared tin. Bake for 20-25 mins or until baked. Testing the centre of the cake, in different areas, with a skewer until it comes out clean.
- Leave in the tin to cool for about 10 mins, before turning out onto a wire rack to cool completely. Or you can leave it in the tin to cool completely before adding the coffee icing.
- Make the Coffee Icing Topping
- Mix the icing sugar and instant coffee powder together. Beginning with 1 tablespoon of preboiled hot water. Start to mix the icing sugar and coffee powder until you have a thick spreading consistency. Adding more water as needed.
- When your cake has cooled completely, spread the coffee icing evenly over your cake.
- Before the icing sets. Decorate with a scattering of walnuts.
- This cake will keep in an airtight container for a couple of days.
- Reduce the amount of coffee powder for a milder flavour.
- Decorate with the chopped walnuts before the coffee icing sets.
- If you are sensitive to caffeine, use decaffeinated coffee/espresso powder