AI tried a new chocolate cake recipe today and it called for 1/3 Cup of Icing sugar and 1/2 Cup castor sugar to be creamed with the butter. I have never seen a recipe with Icing sugar IN the cake batter before. The caked baked up perfectly and tasted great, but can someone tell me what effect the icing sugar is supposed to have? Other ingredients in same recipe are ..butter, eggs, self raising flour, cocoa, baking soda, milk, vanilla and blackberry jam.

I'm sure there are more experienced people on CC that would have a better explanation.  But from my understanding, icing sugar (also known as confectioners' sugar or powered sugar), is the same as regular sugar, but has be "ground" (if that's the correct terminology), to be finer, not having large crystals as other granulated sugars.  Also, icing sugar has a very small amount of cornstarch so it won't clump together since it has been ground into a fine powder.  Confectioners sugar also dissolve into the batter quicker because the crystals are smaller and won't incorporate as much air into the batter (more air = a drier cake I think...).  Hope this helps.

Hi.  I have a book by Carlos Lischetti (cake hero!) and although I can't lay my hands on it right now, I seem to remember that in it he says that he uses icing sugar in all his sponges, saying that it gives a finer crumb.

AThanks guys, the recipe is definitely a keeper. I might have to share it in the recipe section :D