Mocha Marble Cake with Chocolate Covered Coffee Beans
(makes one 18cm round cake, adapted from Martha Stewart's Marble Cake recipe)
For the mocha marble cake:
115g (1 stick) unsalted butter, room temperature, plus more for greasing
220g (1 3/4 cups) cake flour (not self-rising, I used 190g plain flour + 30g (3 1/2 tbsp) cornstarch as per these instructions)
2 tsp baking powder
1/2 tsp salt
225g (1 cup) sugar (I used caster sugar)
3 large eggs, room temperature
1 tsp pure vanilla extract
2/3 cup buttermilk, room temperature
1/4 cup boiling water + 1 tsp instant coffee granules (or 1/4 cup freshly brewed coffee)
1/4 cup Dutch-process cocoa powder
For the mocha icing:
250g salted butter (or unsalted butter + 1/4 tsp salt)
575g (about 4.5 cups) icing sugar , sifted
1/4 cup milk
1 tsp instant coffee granules
1 tsp cocoa powder
Optional: Chocolate covered roasted coffee beans to decorate (I got mine from Captain Coffee)
Preheat oven to 180°C (350°F), grease and line the base of two 18cm round cake tins with baking paper. (You can also use a 20cm tin but the layers will be thinner, I used one 18cm tin and baked one layer after the other) Sift flour, baking powder and salt into a bowl and use a whisk to combine, set aside. Place butter and sugar in a large mixing bowl and beat on high with an electric mixer until light and fluffy. With the mixer on medium speed, add eggs one at a time until combined, scraping down the sides of a bowl with a spatula when needed. Add vanilla and beat again until combined. Add flour mixture in 2 batches, alternating with the buttermilk and beginning and ending with the flour. Place 1/3 of the mixture in a separate bowl.
In a small bowl, mix the cocoa, instant coffee granules and 1/4 cup of boiling water, whisking until it is smooth. Gently mix into the separated bowl of cake batter until combined. Spoon half the vanilla batter and half the mocha batter into the prepared cake tin, and the other half of each batter into the other prepared tin, alternating spoonfuls of vanilla and mocha to simulate a checkerboard. Run a table knife through the batter in each tin to create a swirl effect. Bake for 25-30 minutes or until a skewer inserted into the centre of each cake comes out clean. Cool in tin for 10 minutes and then remove from tin and cool completely on a wire rack. Cakes can be made the night before assembly, wrapped in clingfilm and chilled.
Assemble your cake; if the cakes are slightly domed in the centre you can use a long serrated knife to level the tops of the cake. Place one cake layer on your cake stand and use a spatula to smooth a decent layer of icing over the top of it. Sandwich other cake layer on top and then crumb coat the whole cake with more icing. Chill in the fridge for at least 15 minutes to set the crumb coat. Cover whole cake evenly with the rest of the icing, using an offset spatula to smooth the surface (regularly running the spatula until hot water will help with smoothing it). Decorate the top of the cake with chocolate covered coffee beans. Chill for at least another 30 minutes before serving. Can be stored in an airtight container in the fridge for several days.