Preheat the oven to 180°C and generously butter a 24cm bundt cake tin.

Bring a small saucepan of water to a boil and add the shelled pistachio nuts. Boil for 15 seconds, strain and run under cold water. Once cooled, peel off the husks. Place the nuts in a food processor and pulse lightly to ensure that they are roughly chopped. Remove and set aside.

Cream together the butter, castor sugar and Vanilla Extract until pale in colour. Add the eggs one at a time, mixing well after each addition. Sift together the flour and baking powder and fold into the egg mixture, alternating with the milk.

Divide the cake batter between two bowls. Add the cocoa powder to one batch and the chopped pistachio nuts to the other. Mix both batters lightly to ensure that each cake mixture is well combined. Using two spoons, alternate dollops of chocolate cake mixture with pistachio cake mixture along the bottom of the pan. Repeat with a second layer, ensuring that you alternate, and dollop the pistachio nut cake mixture on top of the chocolate cake mixture, and vice versa.

Place in the oven and bake for about 45 minutes. Check the cake is ready by inserting a skewer in the middle, it should come out clean when removed. Allow to cool completely before removing from the tin.

To make the ganache, melt the butter in a saucepan over low heat. Add the cocoa, castor sugar and cream and whisk until completely dissolved, the mixture should be smooth and glossy. Remove from the heat and allow to cool completely before icing the cake. (When it cools, it thickens slightly to a good pouring consistency. If it is too thick when it reaches room temperature, warm slightly before pouring).