Cream the butter until it is light.
Cream in the powdered sugar, then the vanilla.
Now work in the flour.
Knead the dough on an un-floured board until nice and smooth.
Spray the shortbread pan very lightly with a non-stick vegetable oil spray.
Firmly press the dough into the shortbread pan.
Prick the entire surface with a fork.
Bake the shortbread right in the pan at 325° for about 30 -35 minutes, or until lightly browned.
Let the shortbread cool in its pan for about 10 minutes before you loosen the edges with a knife and flip the pan over onto a wooden cutting board.
If the shortbread does not come right out, tap one edge of the pan.
Cut the shortbread into serving pieces while it is still warm.
Let the pan cool before washing it in the sink or dishwasher.