Preheat oven to 180c.
Mix all plain cake ingredients in a bowl until well combined and set aside.
Mix all chocolate cake ingredients in a bowl until well combined and set aside.
Line the cake tin with a little butter and caster sugar and then add the mixture into sections. Once all mixture has been added, get a knife and lightly mix the cake mixes together.
Bake the cake for 40-50 minutes or until a cake tester comes out clean. Leave it to cool for a minimum of 10 minutes before taking it out the tin and leaving it to rest on a wire rack.