Preheat oven to 325°F. 

Add the butter to a large bowl and blend it until smooth using an electric mixer set at medium speed for about 30 seconds. 

Add the powdered sugar and continue mixing until well incorporated. Scrape down the sides of the bowl and combine thoroughly. 

Add flour and mix at low speed until well blended. The mixture will be crumbled and soft. 

Roll out the dough to approx 1/4 of an inch in thickness, you can knead it a bit just so that the dough comes together, but don't overwork it, then cut into your desired shape. Pierce the shortbread with a fork. I like to use a serrated chopping tool to cut cookies if not cutting shapes.

Line cookie sheet with parchment paper or baking mat. Bake for 12 to 15 minutes, or until just done (slightly golden in color). Do not let them get brown. Remove from the oven. Let cool slightly before placing on cooling rack.