No, room temperature butter is completely wrong.
Your finished dough temperature should be 68°F (20°C). Beating causes friction. Friction causes heat. If you use room temperature butter, the friction will overheat the butter.
Creaming butter and sugar is mechanical leavening, it is not mixing/blending two ingredients. The sugar crystals cut through the butter and create pockets. The water in the dough from the egg creates steam; the water and acids trigger the leavening. Air bubbles from the leavening are then trapped in the pockets in the butter.
The gluten in the flour gives strength and the ability to stretch as the dough rises. Then the starch gelatinization sets the dough.
If the butter is too warm, it will lose it plasticity; it will not be able to hold its shape to trap the air bubbles in the early stages of baking.
In culinary school they teach the correct temperature to cream butter is 65°F. Stella Parks will tell you 60°F. I’ve been using colder butter. The key is getting your FINISHED dough temperature 68°F (20°C).
But if you don’t want to take my word for it, you can read Stella Parks article on the proper way to cream butter.
Does your cookie recipe call for creaming the butter by beating it with sugar? Just how important is that step, and how do you know if you're doing it right? We break down the science of creaming and explain exactly how to do it.
Here I started with butter 48.7°F
The finished dough temperature was 67.6°F
I’ve been baking for 20 yrs, and bake pretty well