Preheat the oven to 180'C.
Roughly chop the walnuts.
Butter your cake tin and line with baking parchment.
In a large bowl, beat the sugar and butter together until pale and fluffy. One by one, beat in the eggs before adding the chicory essence to the mixture. Sift in the flour and the baking powder and then fold the mixture together, adding the walnuts into the batter.
Pour the mixture into the cake tin, transfer to the oven and bake for 30 minutes. Check the centre of the cake with a skewer - if it comes out clean, the cake is ready. Return to the oven for a further 5 to 10 minutes if necessary.
Allow to cool before icing.
Sift the icing sugar into a large bowl and then beat in the butter. Add the chicory essence, combine well and then spread the icing over the cooled cake. Finish by pressing whole walnuts into the icing and cut into slices.
«Make sure to allow the cake to cool thoroughly before topping with icing. The icing will melt if added while the cake is still warm.»