Cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes. Mix in the egg yolk and vanilla extract until smooth.

Gradually add the all-purpose flour and salt to the mixture, mixing until just combined. The dough should be soft and slightly sticky.

Spoon the dough onto a clean surface and shape it into a log. Wrap tightly in plastic wrap and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Slice the chilled dough into 1/4-inch thick rounds and place them on the baking sheet with space between each piece.

Bake for 12-15 minutes until edges are golden brown. Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack.