So many recipes in baking call for superfine sugar rather than the every day sugar that every good American woman has in her pantry. Does it matter?
I've made many cakes that turned out great without the superfine sugar so if you're not looking to be an overachiever in cake baking, then no, it doesn't really matter that much. Regular sugar will work.
But we're not interested in things that simply work now are we? No, we are interested in making the perfect cake... and that's when superfine sugar comes in to play. When you look at the chemistry of baking, sugar is important because it "facilitates the incorporation of air into the fat" (Rose Beranbaum). So since superfine sugar has room for many more sugar crystals, it allows even more air to be incorporated into the fat so that the cake has much better texture.
So basically, think of a cake that you tried one time that completely melted in your mouth and you had absolutely no idea how one could ever achieve that type of cake deliciousness. Superfine sugar can take some of that credit.
This is another basic ingredient of a cake that can confuse people sometimes. There's all purpose flour and self rising flour and cake flour, etc. Does it really matter that much?
YES! Cake flour has a lower acidity than the other flours do and therefore it helps the flavor of the cake to be sweeter and it also does a lot for the texture. The cake will have, as Rose calls it, a "more velvety crumb" (yum!) and allows the cake to support more sugar and other things that you might want to add to your cake- fillings, chocolate, nuts, etc.
All purpose flour can be used sometimes as a sub if you add some corn starch but really, it won't have the same effect.
And if you're thinking about using self-rising flour, put it back in the pantry immediately. It has baking powder in it which will give you a course cake with weak support. It will also make the center fall and you really don't want that.
So to my baker friends out there, make sure to get the right sugar and flour for your cake. You may not think it matters that much but it will be worth it in the end.