In a large bowl place the butter, caster sugar, eggs, cinnamon, flour and baking powder and mix well until smooth. I use a electric hand whisk for this, once all mixed together and when you stop you see bubbles, it will rise. Now stir in the chopped apples you put to the side. If at this point you think the mixture is to thick add a small amount of milk. But this mixture does have to be thick to support the apples.