Most all cookie recipes begin with softened butter. But let's just suppose that you didn't think about getting out your butter last night and here you are, ready to make cookies and your butter is refrigerated. What do you do? (Please don't say "I stick it in the microwave and push the soften butter button!") Guys who build microwaves don't typically bake cookies so if you inquire of any ordinary, garden variety inventor type, he will probably not understand why bakers don't think much of his "soften butter" button. They do enough research to realize that softening butter is something we often do in the kitchen but they don't know why. Here's the deal. Soft butter is still a cream product, while hot butter is melted into an oil. Some people think those two are interchangeable but those people aren't often bakers. Bakers know that once you add heat, you are going to get an entirely different product.
You know those cookies you make from dough you acquire in the refrigerator section of the grocery store? The directions usually tell you to place them 2" apart on a pan when baking because they will spread. Oil. These cookies will go in and come out of the oven exactly the same shape, size and thickness. Butter.
If you ever find yourself with refrigerated butter that needs to be softened, use your cheese grater. You will get lots of surface area that will render that butter soft in minutes.
Also,. don't beat butter with your mixer. Friction creates heat which will break down the creamy consistency that you want. When making cookies, just dump everything into the bowl and set the mixer to STIR. Once there is no danger of catapulting flour all over the kitchen, increase the speed until it is thoroughly mixed.