Creaming the butter--the mixing of the butter and sugar--is one of the most important steps in cake-making. A recipe will often instruct bakers to cream the butter and sugar for somewhere between 3 and 5 minutes. That may seem like a long time, but it is in fact important. Creaming the butter and sugar together actually aerates the batter, leading to a light and fluffy cake. Just be sure to start with room temperature butter and to scrape down the bowl occasionally.