Creaming butter and sugar together is a crucial step in many baking recipes, from cakes to cookies. Creaming adds air into your dough, helps with the structure of the baked good, and acts as a leavening agent.
Most recipes won't give you a precise time for this step and will only say "until light and fluffy." To get to that? First, make sure your butter is at room temperature. Then, you should beat on medium speed for several minutes, making sure to scrape the bowl along the way. To see if it's ready, roll some of the mixture between your fingers: The sugar should be completely dissolved and there should barely be any granules left. Once you've reached that stage, you're good to go.