Coffee and Walnut Cake

Home reconstruction

A British coffee cake is a coffee-flavoured sponge, not an American coffee cake (which is a cinnamon crumb cake eaten with coffee). Worth saying, because the two names collide constantly.

The recipe is a straightforward Victoria-style sponge with one problem to solve: how do you get coffee flavour in without adding water?

Why brewed coffee does not work

A sponge is a balanced system. The flour, fat, sugar and egg are in a ratio, and adding two tablespoons of brewed coffee adds two tablespoons of water to a batter that was not designed for it.

The result is a slightly heavier, damper crumb, and — because brewed coffee is mostly water — not very much coffee flavour for the trouble.

Instant espresso powder dissolved in a teaspoon of hot water gives you many times the flavour for a fraction of the liquid. It is the single change that makes this cake work.

Regular instant coffee will do at a push. Espresso powder is darker and less sour.

The all-in-one method

Mary Berry's contribution to British home baking is largely this: put everything in the bowl at once and beat it. It works because modern baking powder is strong enough not to need the aeration that creaming provides.

Beat for no more than a minute. The risk with all-in-one is overbeating, which develops gluten and toughens the crumb.

Use soft butter. Cold butter will not combine in a single-stage mix and you will beat far too long trying.

Toast the walnuts

Two minutes in a dry pan or five in the oven. Untoasted walnuts are soft and slightly tannic; toasted, they are crisp and sweet and taste of considerably more.

Cool them before they go into the batter — warm nuts melt the butter locally and leave greasy patches.

What you need

Cake

• 225 g soft butter
• 225 g caster sugar
• 4 large eggs
• 225 g self-raising flour
• 1 tsp baking powder
• 2 tbsp instant espresso powder, dissolved in 1 tbsp hot water
• 75 g walnuts, toasted and chopped

Buttercream

• 175 g soft butter
• 350 g icing sugar
• 1 tbsp instant espresso powder, dissolved in 2 tsp hot water
• 8 walnut halves, to decorate

Method

1. 1. Oven to 180°C. Grease and line two 20 cm tins.
2. 2. Dissolve the espresso powder in the hot water and let it cool.
3. 3. Everything for the cake except the walnuts into a bowl. Beat 1 minute until smooth.
4. 4. Fold the cooled walnuts through by hand.
5. 5. Divide between the tins and level the tops.
6. 6. Bake 25 minutes, until risen and springy and a skewer comes out clean.
7. 7. Cool in the tins 5 minutes, then on a rack completely.
8. 8. Beat the buttercream ingredients until light, 3 minutes.
9. 9. Sandwich and top, and press the walnut halves round the edge.

Completely cool means completely

Buttercream on a sponge that is even slightly warm melts, slides, and soaks in. The cake then looks collapsed and the layers slip.

An hour on a rack, and longer if the kitchen is warm.

Why two tins rather than one split cake

Two thinner sponges bake evenly and quickly. One deep cake takes nearly twice as long, and by the time the middle is done the outside is dry.

Splitting a deep cake also gives you a domed top to level off, which is waste.

Storing

Three days in an airtight tin at room temperature. Do not refrigerate — cold turns buttercream hard and dries the sponge.

The unfilled sponges freeze well for three months, wrapped. Fill after thawing.