Creaming Butter and Sugar...
Many baking recipes call for "cream the sugar and the butter until light and fluffy..." What does that mean, and why do we need to do that? The first thing to understand is that if you fail this step, there is just no way you are going to get the airy light texture you are seeking in your final baked goods. If you are a cookie fan, keep on reading...
So Do This...Whenever a recipe call for creaming sugar and butter together until light and fluffy, bring your butter to the exact temperature of 60 degrees Fahrenheit. Use a food processor to do the creaming (it requires a lot of energy). With a 450 horsepower Kitchen Aid, it takes approximately five minutes on medium speed to cream 8 ounces (half a cup) of butter and sugar, in a 70 degrees Fahrenheit kitchen, to the correct light and fluffy stage.
Creaming results in the water molecules present in the butter to dissolve the sugar while air is trapped by the fat molecules present in the butter. Under-creaming results in not enough air being trapped causing too much density in the dough; over-creaming results in too much air being trapped causing a "collapse" of the dough structure. The temperature of the butter is absolutely critical. The sugar will be at room temperature (70 degrees Fahrenheit). Butter starts to melt at 90 degrees Fahrenheit, but its ability to stretch and expands tops off at 68 degrees Fahrenheit. Using butter any warmer than 68 degrees Fahrenheit will not work, you will not be able to trap the air (never used melted butter to cream sugar). By using butter at exactly 60 degrees Fahrenheit, the addition of sugar at room temperature (warmer) and the mechanical heat caused by the food processor ensure the butter will never get warmer than 68 degrees Fahrenheit.
Final Takeaway...creaming is not about combining (stirring, mixing, beating) ingredients, it is about aerating them (trapping air in a structure). It is a critical step in the final texture of baked goods. When heated, the air molecules expand, gently rising the dough. The temperature of the butter and the duration and intensity of the creaming determine how much air gets trapped. That amount of air being trapped is what the Chef must control.