In a large bowl, beat the butter, sugar and salt with an electric mixer for 2 minutes, until pale and fluffy. Beat in the egg yolk and vanilla.
Add the flour and stir just until you have a soft dough. Shape it into two or three logs, wrap and refrigerate for an hour (or up to a few days) or freeze for up to 6 months.
When ready to bake, let sit on the countertop until it softens a bit, then slice 1/4" thick, press with a cookie stamp (if you like) and bake on a parchment-lined sheet at 350F for 12-14 minutes, or until pale golden around the edges. Transfer to a wire rack to cool.