In a medium to large mixing bowl, cream together the butter and sugar.
Stir in the egg yolks and vanilla extract.
Add the flour and salt. Stir until a soft dough forms.
If you are not planning to shape or press the cookies, then roll the dough into a log shape and cover in plastic. Freeze for at least 30 minutes, and up to overnight.
If you would like to shape or press the cookies, then roll the dough out on a lightly floured surface and do so. Place them on a lined baking sheet after. Then freeze for at least 30 minutes and up to overnight.
Bake at 350°F for 8-10 minutes, until the edges begin to brown.