Preheat oven to 160°C and line a deep 22cm cake tin with baking paper
Melt butter, chocolate and coffee with the hot water in a saucepan over low heat until smooth
In a bowl sift the flours, bicarb and cocoa, then mix in the sugar
In another bowl whisk the eggs, oil and buttermilk
Add the wet ingredients to the dry ingredients and whisk together
Gradually whisk in the chocolate mixture
Pour into the tin and bake for about 1 hour 45 minutes, until a skewer comes out slightly moist
Leave to cool completely in the tin
Melt the butter and chocolate together, let cool slightly, then pour over the cake and let it drip down the sides
