In a large mixing bowl, beat together 1 cup of softened unsalted butter, ¾ cup of granulated sugar, ¼ teaspoon of salt, and 1 teaspoon of pure vanilla extract until the mixture is smooth and creamy. This should take about 2-3 minutes. Next, add 1 egg yolk and mix until fully incorporated. Gradually stir in 2 cups of all-purpose flour until just combined, taking care not to overmix.

Turn the dough onto a lightly floured surface and knead into a log shape, about 2 inches in diameter. Wrap in plastic wrap and refrigerate for at least 2 hours.

Preheat your oven to 325°F (160°C) and line your baking sheets with parchment paper.

Remove the chilled dough and slice into ⅛-inch thick rounds, placing them 1 inch apart on the baking sheets. Bake for 16-18 minutes until the edges turn golden brown.

Cool the cookies on the sheets for about 5 minutes before transferring to a wire rack to cool completely.