Mocha Hazelnut Marble Cake with Mocha Mascarpone Ganache
slightly adapted from here
For the Cake:
2¼ cups plain flour (I use "00" flour)
½ cup toasted hazelnuts, finely ground
1 teaspoon baking powder
1 teaspoon fine sea salt
225g unsalted butter, at room temperature and divided
75 dark chocolate, coarsely chopped
60ml espresso coffee
1 teaspoon instant coffee
1¾ cups golden caster sugar
4 eggs, at room temperature
2 teaspoons vanilla extract
1 cup buttermilk, at room temperature
For the Ganache:
125g dark chocolate, chopped
60ml light corn syrup
½ teaspoon vanilla extract
60ml espresso coffee, at room temperature
Make the Cake:
Preheat the oven to 180°C. Generously butter a 2½ litre bundt pan and dust the inside with cocoa powder, tapping out the excess.
In a mixing bowl, whisk the flour, hazelnuts, baking powder and salt together. Set aside.
Put 30g of the butter into a heatproof bowl along with the chocolate, coffee and instant coffee. Put the bowl over a pan of gently simmering water. Stir the mixture until melted and smooth. Remove from the heat.
In the bowl of an electric mixer fitted with the paddle attachment, beat the remaining butter with the sugar on medium speed for about 5 minutes. Add the eggs one at a time, beating well after each addition. Reduce the speed of the mixer to low and add one third of the dry mixture, followed by one third of the buttermilk and continue in that manner until all the dry mixture and buttermilk have been added.
Spoon half of the batter into a bowl and add the melted chocolate mixture to it, using a rubber spatula to mix it thoroughly.
Pour all of the plain mixture into the prepared pan and top with the chocolate mixture. Use a butter knife to swirl the two batters together, creating the marbled effect.
Bake for 65 to 70 minutes, or until a skewer inserted into the middle comes out clean. Leave the cake to cool in the pan for 15 mintues before turning out on a wire rack to cool completely.
Make the Ganache:
Put chocolate into a heatproof bowl. Put the bowl over a pan of gently simmering water. Stir until melted and smooth. Remove from the heat and stir in the mascarpone. Add the corn syrup and vanilla and stir until combined. Gradually add the coffee and stir to create a thick, spreadable ganache. Spread on top of the cooled cake.