The Creaming Method
Many baking recipes, especially those for cakes and cookies, call for ingredients to be creamed. In this method, butter and sugar are blended together until smooth. This step softens the butter and removes the lumps so that the remaining ingredients will blend evenly and thoroughly.
If you use a standing electric mixer, use the paddle attachment, not the whip. (The whip is designed for adding air, not creaming.) If you are creaming by hand, soften the butter slightly and use a large wooden or metal spoon, pressing the butter against the side of the bowl.
The sugar is an important element in creaming. Its crystals cut into the fat tunneling air through, thus speeding the process. If your recipe has sugar, add it in the beginning to help the creaming along.
Be aware that this step can be taken too far. Butter is fat and fat melts with heat, including heat from friction.
In the oven the fats melt. If a batter goes into the oven cool, other protein rich ingredients such as eggs and flour solidify and hold the batter together. But if the fat goes in to the oven already warmed up, it will melt and spread before the proteins have a chance to set.
Over-creaming is responsible for cookies that spread too far and cakes and quick breads that come out greasy, wet, and chewy.
Friction is important to soften the fat so that the remaining ingredients can be blended evenly. But if you’re not paying attention, friction can build up to a point that liquefies the fat. The phenomenon gets worse if you start the recipe with room temperature, softened butter.
For proper creaming use cold butter and cream it only until the lumps are gone, no more. If you cream by hand with softened butter, don’t over-do it, and chill the batter before baking if it seems too wet.