Having thought this through, I understand that the above may be inaccessible to the majority of American readers.
I found this online - Brie Barton's blog
on a wing and a prayer
She references the Hummingbird Bakery, of whom I am also a fan.
So this recipe is different, untested by me, but will probably be easier to follow.
2 tbsp instant coffee granules (espresso powder makes a great rich taste!)
450 g (2 cups) unsalted butter at room temperature
450 g (2 1/4 cups) caster sugar (white sugar)
6 large eggs
450 g (3 1/2 cups) plain flour (all-purpose or cake flour)
2 tbsp baking powder
2 tsp cocoa powder
1/2 cup of walnuts crumbled, plus half walnuts to decorate (optional)
1 quantity frosting
250 g (2 1/4 cups) icing sugar, sifted
80 g (5 tbsp) unsalted butter, room temperature
25 ml (2 tbsp) heavy cream
a few drops of vanilla extract
1 tbsp instant espresso mixed with 2 tbsp boiling water
25 cm ring mould (known as a bundt pan in north america)
to make cake:
to make 'coffee essence' put instant coffee and 170 ml (3/4 cup) of water in a small sauce pan, bring to a boil and reduce by half. set aside to cool completely.
preheat oven to 170 C (325 F)
beat together butter, sugar and coffee essence. add eggs one by one, mixing well and scraping the bowl down as you go. beat in flour, baking powder and cocoa powder, mix until batter is light and fluffy. fold in crumbled walnuts.
pour mixture into prepared mould and even with spatula. bake for 40 minutes in preheated oven or until the sponge feels firm to the touch. (do not open oven door during early cooking or you will collapse the the cake). cool slightly in mould before turning out onto a wire rack to finish cooling completely.
to make frosting:
beat icing sugar and butter until mixture comes together. in a small bowl combine cream, vanilla and instant espresso. add wet ingredients to sugar and beat until light and fluffy (5 minutes).
cover top of cooled cake with frosting, decorate with walnut halves