Pistachio mocha marble cake

We're off for a girls weekend, six of us staying with our friends Liz and Dilly in Plymouth.  I'm looking forward to long walks on the moors, gin cocktails and a good catch up. This is my contribution to our Friday night feast - a marble cake made with one half espresso and cocoa flavoured, the other made with toasted, ground pistachios. I topped it with a coffee buttercream icing and decorated it with the bigger chunks of ground pistachios too big to sift into the cake batter.  A marble cake is a good cake to make when you can't decide which flavour to go with - make both!

Ingredients

1 tbsp instant espresso powder

1 tbsp boiling water

5 oz pistachios

10 oz margarine

10 oz caster sugar

5 eggs

10 oz self-raising flour

1 tsp baking powder

2 tbsp cocoa

1 tsp vanilla essence

For the icing

3 tsp instant espresso powder

1 tsp boiling water          

4 oz butter, softened      

8 oz icing sugar 

Method

1. Preheat the oven to 175°C and grease a 9” round cake tin.
2. In a mug, mix the espresso powder and boiling water together to form a smooth paste, then set aside to cool.
3. Spread the pistachios out on a baking sheet and place in the oven for a few minutes to toast – keep a close eye on them as they will burn quickly.
4. Remove from the oven and transfer the nuts to a food processor and blitz until fine.
5. In a large mixing bowl, cream the margarine and sugar until pale and fluffy.
6. Beat in the eggs, one at a time, adding a spoonful of the flour after each addition.
7. Sift in the flour and baking powder and fold it gently into the batter.
8. Scoop half of the mixture into a separate bowl.
9. In one portion, sift in the cocoa powder, and stir the espresso paste until thoroughly combined.
10. In the other portion, sift in the ground pistachios. Set aside any larger pieces that won’t pass through the sieve. Add the vanilla essence and fold together well.  
11. Spoon large blobs of each cake mixture into the prepared tin, alternating the flavours to give a marble effect. Bake for 50-60 minutes until the cake is springy to the touch and a cake tester comes out clean.
12. Allow the cake to cool in the tin for ten minutes, then turn out onto a wire rack and cool completely.
13. To make the icing, place the butter in a mixing bowl and sift in the icing sugar. Dissolve 3 tsp instant coffee in 1 tsp boiling water and beat butter and icing sugar, until light and creamy.
14. Once the cake has cooled, use a palette knife to spread the icing all over the cake, and then decorate with the reserved ground pistachios.