Since I was a kid making Christmas cookies, this common cake and cookie recipe instruction would stump me: "cream the butter and sugar until light and fluffy." I did the best I could with the old hand mixer we had, but always wondered, 'do they really mean light and fluffy?' How could a stick of butter and some sugar ever be anything but thick and heavy?
In culinary school, I was coached through the technique and finally got it. The butter and sugar will never transform into cotton candy, but if the butter is at room temperature to start with and is beaten it long enough (which can take several minutes with a hand mixer), tiny pockets of air will form in the mixture and help give the cookies or cake a little extra lift.
Please see the slideshow below for a detailed demonstration of this technique. You can apply it to the chocolate chip cookie and moon pie recipes from earlier posts.