Creaming Butter and Sugar Is About Air

Photo by Rob Wicks on Unsplash

Beating softened butter and sugar together isn't just combining ingredients — sugar crystals cut tiny air pockets into the butter's fat structure, and those pockets become the seeds that expand into a light, fine crumb once leavening gas fills them in the oven. Butter that's too cold won't hold enough air; butter that's too warm or melted collapses the structure instead of trapping it. Under-creaming is one of the most common reasons a cake or cookie turns out dense.