Beat the butter and sugar until light and fluffy

Add eggs, one at a time,incorporating fully before adding the next.

Stir in vanilla extract and buttermilk

In a separate bowl,Sift flour, baking powder and baking soda / bicarbonate of soda together

Whisk ⅓ flour mixture into the wet mixture, combine well and fold in the remaining flour.

Divide batter in half and stir in cocoa powder and dissolved coffee through one half

To get the marbled effect, place the batter in a checkerboard like formation. start by alternating the vanilla and chocolate batters to create a rough checkerboard along the bottom of the pan. Then repeat with a second layer, being sure to place the chocolate batter on top of the first layer's vanilla batter and vice-versa.

run a wooden spoon handle or really thick skewer through the batter to create the swirls.Do not overmix.

Remove cake from tin and cool on a wire rack.

When cooled, frost with the prepared ganache. Dust with cocoa powder if you prefer.

Chop chocolate into small pieces. Place in a l bowl and set aside.

Heat the cream in a saucepan over medium heat. As soon as it begins to simmer, immediately remove from the heat and pour over the prepared chocolate.

Allow to stand for 5 minutes, then lightly stir with a whisk until all of the chocolate has melted and the mixture is smooth. Allow to set at room temperature for 10 minutes before pouring evenly over the cake.