In a large bowl or standing mixer cream softened butter until fluffy, about one minute.
Add the flour and powdered sugar to the bowl and beat on low-medium, with a paddle attachment, for 10 minutes. This is important because it gives the cookie dough a whipped consistency.
Chill the dough in the refrigerator for 30 minutes to an hour so it's workable and not too sticky.
Take the dough out and slightly knead it to form a ball. From here you can pinch off and make 1-inch cookie dough balls or roll out the dough to cut cookies.
To make Shortbread Cookies: Flatten each round dough ball slightly and press a fork into the top to create lines and add sprinkles.
To make Thumbprint Cookies: Keep the ball shape and press a dome (using your thumb or a ½ tsp measuring spoon) into the center and fill with thick preserves.
Place them on a baking sheet lined with parchment paper and bake for 10-15 minutes at 350 degrees F until set and golden around the edges. Let cookies sit on the pan 2-3 minutes and then carefully transfer them to a cooling rack.
This recipe will yield 15-20 cookies depending on how large you make the cookies!