I hunted all over for a 20cm square coffee and walnut cake recipe because my oven is small and two round tins won’t sit side by side. I didn’t have much luck so this is my own recipe, inspired by many, many others (listed in the credits).
A square tin is trickier than two round ones; there’s a narrow window where the centre of the cake has cooked through and the edges haven’t overcooked. In my oven this takes 35 minutes and the edges, particularly the corners, soften more the next day so don’t panic if you think you’ve overdone it.
Felicity Cloake’s How to Make the Perfect Coffee and Walnut Cake was the most useful recipe I found. She uses soft brown sugar, adds double cream to the buttercream icing and includes salt (which can reduce the bitterness in coffee*).
The cream is optional; I rarely buy it but it’s a nice addition. I've used fresh and defrosted cream - both make the icing a little grainy-looking but it's worth it for the taste.
I use salted butter and kosher salt. Generally unsalted butter is recommended for baking but I always use salted and no one has ever complained.
If your coffee granules refuse to dissolve in the hot water (mine always struggle), put them into the microwave for 5-10 seconds.
Coffee and walnut cake
- 100g walnuts
- 175g room temperature butter (plus more for greasing. I use a 50/50 mix of Stork and butter)
- 175g soft, light brown sugar
- 3 large room temperature eggs
- 175g self-raising flour
- 1 tsp baking powder
- a pinch salt (around an ⅛ tsp)
- 2 tbsp instant coffee (I use Douwe Egberts)
- 2 tsp hot water
- 2 tbsp milk (any, I use soya)
- 125g room temperature butter
- 125g icing sugar
- 1 tsp instant coffee (I use Douwe Egberts)
- ½ tsp hot water
- 4 tbsp double cream (optional)
- a small handful of chopped walnuts to decorate (around 30g)
You will need
- a 20cm loose-bottomed square cake tin
- Preheat your oven to 180°C (160°C fan). Line a 20cm loose-bottomed square baking tin with greaseproof paper and generously grease the sides with butter. Tip 100g of walnuts onto a lined baking tray and bake for 10 minutes then roughly chop and set to one side.
- Cake: In a large bowl, cream 175g of room temperature butter and 175g of soft brown sugar together until combined (I use a hand-held mixer). Add 1 egg at a time (3 eggs in total) to the butter and sugar mixture, continually whisking.
- In a medium bowl, combine 175g of self-raising flour, 1 teaspoon of baking powder and a pinch of salt then sift a quarter of the flour mixture into the egg mixture and whisk. Repeat until all the flour has been used up.
- In a small jug, dissolve 2 tablespoons of instant coffee granules in 2 teaspoons of hot water then add 2 tablespoons of milk. Whisk the coffee mixture into the batter until combined then stir in the chopped walnuts. Scrape the batter into the prepared cake tin, smoothing the top with a spatula.
- Transfer to the oven and bake for 30-35 minutes. I check the cake after 25 minutes, rotate it and loosely cover the tin with foil if the cake has already browned. The cake is done when a skewer comes out clean.
- Once the cake is ready, allow it to cool in its tin for 10 minutes before turning out onto a rack.
- Icing: In a medium bowl, use a wooden spoon to mix 125g of room temperature butter and 125g of sifted icing sugar. In a small bowl or jug, dissolve 1 teaspoon of instant coffee granules in ½ teaspoon of hot water, add 4 tablespoons of double cream (optional), then stir the coffee mixture into the icing.
- Once the cake has cooled completely, spread the icing over the cake and top with 30g of chopped walnuts. Store the cake in an airtight container for up to 3 days.