Preheat your oven to 325°F (160°C).
In a large bowl, cream the softened butter and powdered sugar until smooth.
Gradually add the flour and salt, mixing until just combined.
If using, stir in the vanilla extract.
Turn the dough out onto a lightly floured surface.
Roll it out to about 1/4 inch thick.
Use cookie cutters to cut out shapes and place them on a baking sheet lined with parchment paper.
Prick the tops of the cookies with a fork for decoration.
Bake in the preheated oven for 18-20 minutes, or until lightly golden.
Allow to cool on a wire rack before serving.