Walnut espresso layer cake

This is a slightly adapted Walnut Espresso Layer cake from Outsider Tart's Baked in America that I made for my boyfriend's mum's birthday. I asked her what flavour cake she would like and she said coffee; since she gave me the Outsider Tart book for my birthday a few weeks before, I thought it would be nice to make something from that.

Outsider Tart's Walnut Espresso Layers Cake
Ingredients
walnuts - 9oz/ 250g/ 1.5 cups
all-purpose or plain flour - 20oz/ 550g/ 3.75 cups
baking powder - 1.5 tsp
bicarbonate of soda- 1.5 tsp
kosher salt - 0.75 tsp
instant espresso powder - 3 tbsp
buttermilk, at room temperature - 8 fl oz/ 240ml / 1 cup
brewed triple strength espresso - 6 fl oz / 175 ml/ 0.75 cup
vanilla extract - 1 tbsp
unsalted butter, softened - 12oz/ 340g / 1.5 cups
granulated sugar - 12oz/ 340g / 1.5 cups
light brown sugar - 6oz / 175g/ 0.75 cup, packed
large eggs - 6

Preheat the oven to 180 C/ 350 F/ gas mark 4. Butter three 9in/ 7.5cm round cake pans, line the bottoms with baking parchment, dust with flour and tap out any excess.

In a food processor, pulse the walnuts until finely ground. It's better to pulse versus running the motor to avoid making a paste.

Whisk together the flour, baking powder, bicarbonate of soda, salt, espresso powder and the ground walnuts.

In a large measuring jug combine the buttermilk, brewed espresso and vanilla. Set both aside.
In a stand mixer, cream together the butter and both sugars on medium-high speed until light and fluffy, about 5-6 minutes. Add the eggs one at a time, beating thoroughly after each addition. Scrape the bowl as you go.

On low speed, alternately add the flour/nut and buttermilk mixtures in 3-4 additions until just combined. The batter may have a slightly curdled appearance, which is just fine. Divide the mixture evenly among the prepared pans.

Bake for 30 to 35 minutes, or until a knife inserted comes out clean. It's best to rotate the pans front to back, top to bottom, about three quarters of the way through. Cool the layers in their pans for about ten minutes before turning them out on wire racks to cool completely.

This is in fact where the recipe ends, as the book has a separate chapter on frostings. I couldn't find a coffee flavour frosting so I decided to make a normal buttercream and flavour it with coffee - though it didn't have a strong a flavour as I would have liked, as that was the point when I ran out of coffee!

I have to admit that I don't actually drink coffee, and so only keep instant in the house, and didn't particularly want to buy espresso powder just for this cake, so I - whispers - used instant coffee where the recipe specified espresso. I'm sorry, Outsider Tart! Hope you forgive me... the cake tasted pretty good anyway!

I also decided I didn't need a massive cake as it was only going to serve a few people, so I made 2/3 of the recipe quantity and only made two layers instead of three - it still turned out to be a fairly deep cake.
I assembled the layers like this

I filled a piping bag with the buttercream

And piped a swirly pattern on the top. But this somehow just wasn't enough for a birthday cake and I tried to think of a way to decorate it...

... and hit on the idea of maltesers! I arranged them in two circles and also inserted some florists' wire into a few maltesers and stood them in the top of the cake, which was an idea I saw on the internet somewhere. I really like the way it turned out!

Walnut and Espresso Layer Cake recipe from Baked in America by David Muniz and David Lesniak, published by Ebury Press. Used by permission of the authors, The Random House Group Limited and Rizzoli International Publications, Inc.

(Photographs are my own)
The book can be purchased on Amazon, Random House or Outsider Tart.

As the letter for this month's Alphabakes challenge is W, I am entering my walnut and espresso layer cake. I am also sending it to Cupcake Crazy Gem's United Bakes of America blogging challenge, as Outsider Tart is an American bakery in London and the recipe book, Baked in America, is full of goodies from there.