Pre-heat the oven to 180°c and grease and line 2x20cm cake tins with butter and baking paper.
Sift together the sugar, flour, cocoa powder, baking powder, baking soda and salt into a large bowl.
In a jug, combine the eggs, buttermilk and melted butter and mix well.
Pour into the dry ingredients and mix well.
Dissolve the peanut butter into the hot coffee and pour into the cake batter and mix well.
Divide the batter between the prepare pans and place in the pre-heated oven.
Allow to bake for 30-35 minutes until a skewer inserted comes out mostly clean with a few moist crumbs.
Remove from the oven and allow to cool before removing from the tins.
To make the icing, melt the chocolate then beat with the butter until well combined.
Sift in the icing sugar and cocoa powder and beat until light and fluffy.
Add the coffee and mix well.
To make the praline, bring the water and sugar to a boil in a small saucepan, whisking over medium heat until the sugar dissolves. Turn the heat up and allow to boil, washing down the sides of the pot with a pastry brush and clean water to prevent the syrup from crystallising.
In the meantime, line a baking tray with baking paper and place the pistachios on top.
When the syrup has reached a deep amber colour (approximately 10 minutes of cooking), pour it over the pistachios.
Allow the praline to cool completely and harden before blitzing in a food processor to create the pistachio praline.
Spread a little of the icing onto one of the cakes followed by some of the pistachio praline then place the other cake on top, then using the rest of the icing, cover and decorate the entire cake.