For the cake:
225g plain flour
85g cocoa powder
1½ tsp baking powder
1½ tsp bicarbonate of soda
2 tsp vanilla extract
250ml boiling water
For the icing:
300g plain chocolate (70%)
300ml cream (double or whipping)
Preheat oven to 180oc and line two baking tins (200mm diameter).
Mix all of the cake ingredients, except the boiling water, in a large bowl until smooth and well combined.
Add the boiling water to the mixture, a little at a time, until smooth and very liquid.
Pour the mixture into the two baking tins and bake in the oven for 25-35 minutes, or until the top is firm to the touch and a skewer inserted into the centre of the cake comes out clean, leave the cakes to cool in the tins.
Whilst the cakes are baking prepare the icing:
Break the chocolate to pieces and place in a saucepan with the cream. Put the saucepan on low heat and stir gently until the chocolate has melted and the mixture is smooth. Leave the mixture to cool for 1-2 hours, or until thick enough to spread over the cake.
When the cakes and icing has cooled, remove the cakes from the tins and place one cake up side down on a serving plate.
Spread an even layer of icing over the top. Then carefully place the second cake on top and ice the cake all over with the chocolate icing, using a palette knife.
Keep in the fridge until serving.