Many baking recipes call for “softened” butter, or room temperature butter. The reason for using softened butter is that you want to beat the butter (also called “creaming the butter”), either with sugar or without, and it’s very hard to beat a cold stick of butter.
The best thing to do to soften your butter is to put it out on the kitchen counter for an hour before you have to use it. But sometimes we don’t think that far ahead. One popular solution is to put the cold butter in the microwave for 10 to 20 seconds. The problem with microwaving butter is that the microwave can heat the butter unevenly, and tends to over-soften or even melt the butter in places. You want pliable butter for beating, not almost melting butter.
Here’s a simple trick to soften butter quickly using some wax paper and a rolling pin.
Just put the stick of butter between two large pieces of wax paper. Using a rolling pin, press down on the butter. Roll it out they way you would roll out a pie crust. When the butter is about 1/8 to 1/4-inch thick, lift off the wax paper and peel away the butter (before it gets too soft to peel).
Voilà! Softened butter, ready for beating.