Preheat your oven to 350° now or while the dough is in the fridge. Be sure your oven is fully at the right temperature before baking cookies.

In the bowl of a mixer beat butter until it's light and smooth.

Add in powdered sugar and vanilla extract and mix completely.

Mix in flour and salt (if adding) and beat until all ingredients are incorporated, scraping down the sides and bottom of the bowl so everything is mixed well.

Roll cookie dough into a ball and flatten it to a disk shape.

Wrap in plastic wrap and refrigerate the wrapped dough for 15 minutes. (If you refrigerate the dough longer allow it to warm a few minutes on the counter before rolling or it will crack easily)

Roll out scoops of dough and roll in between hands for drop cookies or roll out dough in between wax paper sheets to 1/4" thick and cut with cookie cutters.

Place cookies on parchment-lined baking sheets.

Place baking sheets in the refrigerator for 10 minutes.

Then bake each baking sheet for 15 minutes. The cookies should be fairly pale, and lightly golden on bottoms or edges is ok, do not over-bake or brown shortbread, it will become dry and crumbly,

Let the cookies cool completely on the baking sheets before moving them. Remember they are dryer cookies and will be more tender and break easier if handled too much before they are completely cooled.