The inspiration for this cake recipe comes from a similar item that I had in Starbucks in Singapore a few years ago. The Starbucks version was yummy but also sickly sweet, and I was reminded of it when a friend at work asked me to make a cake with nuts in it.
Originally I thought of making a coffee and walnut cake, but then I thought why not try the stack ? I haven’t made a many layered creation like this before, so I knew it would be a worthy challenge.
I used an 8 inch square (20cm) cake tin with a removable bottom. I am sure it can also be made with a round tin and served as wedges, but I think that the rectangles look nicer. I lined the tin with baking parchment in both directions so that when the cake was done, I could lift it out with the parchment. This makes it adaptable to a square tin without a removable bottom too.
Make the chocolate cake a day in advance. Like bread, it is much easier to slice if it is not fresh out of the oven. I sliced my cake into three horizontal slices, but on reflection, maybe I should have used 4 slices. Use your favourite chocolate cake recipe, the darker the better.
If you go for a packet mix, choose one without filling and frosting, and preferably one that uses oil as an added ingredient. Vegetable oil will make the cake very moist.
I also made my caramel a day in advance – I chose to make dulce de leche, where you simmer a can of condensed milk (just place the whole tin in the water, don’t open it) for 3 hours. This is a fairly simple method, just check to make sure that it doesn’t boil dry.
Use the same baking tin to assemble the cake – I re-lined mine with parchment for ease.
I made the base from digestive biscuits and melted butter – like a cheesecake base. You can use dark choc biscuits if you like, but I thought that oaty digestives would give another texture. You need approximately half the weight of butter to biscuits e.g. if using 150g biscuits, melt 75g butter. Whizz up the biscuits to crumb consistency using either a food processor or by bashing them with a rolling pin while they are in a plastic bag. Slowly mix in the butter and line the base of your tin with the mixture – use the base of a glass or cup to push the mixture down – push it into the corners, then put the whole tin in the fridge so that the base sets more firmly as the butter hardens.
Next slice the cake so that it is ready to layer – be careful because each layer will be quite flimsy – you can put parchment between the layers if it helps to lift them.
Now make the mousse and buttercream – each amount should make enough for two layers.
200g dark chocolate (70% at least)
1 1/2 cups thick cream
2 tablespoons of icing sugar
Using an electric whisk, whisk the cream and icing sugar in a chilled bowl preferably until the cream is stiff rather than runny. While you are doing this, melt the chocolate in a bowl over a double boiler.
Once the chocolate has melted, fold half of the cream into it, it might go a bit stiff and claggy at first, but keep folding and it will smooth out. Then fold in the rest of the cream until it is an even consistency.
1 cup unsalted butter – soft
1 heaped cup of smooth peanut butter
2 cups of icing sugar sifted
1/2 cup thick cream
a pinch of salt
Using an electric whisk, whip the butter and peanut butter until light and fluffy. Next whisk in the icing sugar. Now whisk in the cream and salt – if it is too stiff to spread, add a little more cream.
When I assembled my cake, I placed choc mousse over the biscuit base, followed by a layer of cake, followed by a layer of peanut butter cream, followed by a layer of cake, then a layer of mousse. I carefully placed some peanut butter cream on top of the mousse (this is why I could have done with another cake layer), and finished off with a layer of cake. I lightly whisked the dulce de leche with a fork and spread that over the top with a spatula. Then I sprinkled salted peanuts on top. I placed it in the fridge for a few hours before removing from the tin and slicing.