Cream the softened butter and granulated sugar in a mixing bowl until light and fluffy.

Incorporate the egg yolk and vanilla extract into the creamed butter.

Sift the flour and salt into the bowl, mixing until a dough forms.

Shape the dough into a log approximately 5 centimeters in diameter, wrap in plastic, and chill for 60 minutes.

Preheat the oven to 180°C (350°F) and line a baking tray with parchment paper.

Slice the chilled dough log into 1-centimeter thick rounds.

Place rounds on the baking tray and brush with a mixture of the second egg yolk and milk.

Score the tops with a fork and bake for 12 minutes until golden.

Cool completely on a wire rack.