Preheat the oven to 180°C/160°C fan oven/Gas Mark 4. Grease and line 2 x 8” round cake tins. Place the coffee granules in a jug and add the boiling water, stir until the coffee granules have dissolved and leave to one side.

Place the margarine and sugar into a bowl and cream together until smooth. Add the eggs and beat into the creamed mixture, if the mixture begins to curdle add a spoonful of flour.

Gently sieve the flour on top of the mixture and fold in and finally fold in the coffee.

Divide the mixture between the prepared cake tins and bake in the oven for 25–30 minutes until risen and skewer inserted into the centre comes out clean. Leave the cakes to cool in the tins for 15 minutes and then remove and place on a wire rack to cool completely.

Whilst the cakes are cooling make the buttercream. Place the coffee granules into a jug and add the boiling water, stir until the coffee granules have dissolved and place to one side.

Place the butter in a bowl and beat until glossy. Add half the icing sugar beat into the butter, once incorporated add the remaining icing sugar and continue to mix the buttercream. Add the coffee mixture and beat the buttercream until light and fluffy in texture.

Once cooled flatten the top of one of the cakes, using a serrated knife. Place half the buttercream into the sponge you have flattened and spread the evenly cover the sponge. Sandwich the other layer of sponge on top with the domed side facing up. 

Spread the remaining buttercream on top of the cake. Sprinkle the walnuts around the top edge of the cake and sprinkle the chopped chocolate on top of the cake. Your cake is not ready to serve and enjoy!