1. Preheat oven to 175 degrees C.
2. Butter two 8-inch round cake pans and line the bottoms with parchment paper discs.
3. Whisk all the dry ingredients together well in a large bowl.
4. In a separate bowl, whisk together all the wet ingredients.
5. Slowly add the wet ingredients to the dry ingredients, mixing as you go. Mix everything until there are no pockets of dry flour left. The batter will be very thin.
6. Divide the batter between the two cake pans, and bake for 35 minutes until risen and a toothpick inserted into the center of the cake comes out without wet batter clinging to it.
7. Leave to completely cool and frost. Grated extra Cadbury chocolate over the cake.

Frosting Method

1. Melt the butter in a small sauce pan over low heat.
2. Add the cocoa and chocolate, stir until the mixture is smooth and thick.
3. Remove the pan from the heat and place the cocoa mixture into a medium size bowl. Let it cool slightly.
4. Add the milk and vanilla with the powdered sugar to the bowl and beat with an electric mixer or whisk until you have the spreading consistency you desire.
5. You can adjust the quantities according to your liking.