Preheat the oven to 350 F/176 C. In a large bowl mix together the flour, butter, sugar, and optional salt and vanilla extract, using a hand mixer, stand mixer, fork, food processor or pastry blender. Mix until the dough is all crumbly, and blonde in color.
Bring the dough together and knead it a little bit, then shape it into a ball or log. Cover it and chill it in the fridge for 15 to 20 minutes. While chilling the dough isn't necessary, I usually do, because it helps when shaping it.
There are several ways to form the cookies. Roll out the dough until it is about 1/4th of an inch thick and use a round or rectangle cookie cutter, or take a couple of tablespoons of it and roll it into a ball and then press your thumb into it. If doing the thumbprint kind, fill each cavity with about a tsp. of jam or jelly.
Now bake the cookies on the middle rack for 12ish to 16ish minutes for the thicker thumbprint style cookies or 10ish minutes for the smaller flatter classic style of shortbread cookies. They are done with slightly brown on the bottom edges.
Remove the cookies and allow them to cool on the cookie sheet for a few minutes, then transfer them to a wire rack to cool completely.
You can eat them as is, or dust them with powdered sugar, dip them in chocolate, or drizzle a powdered sugar and milk glaze over them. Up to you. Enjoy!