In a large mixing bowl, beat 1 cup of softened unsalted butter and ¾ cup of granulated sugar together on medium speed until creamy and lightened in color, about 2-3 minutes. Add ½ teaspoon of salt and 1 teaspoon of pure vanilla extract, mixing until combined. Incorporate 1 large egg yolk until smooth.

Gradually sift in 2 cups of all-purpose flour into the butter mixture, mixing on low speed until just combined. Be cautious not to overmix; the dough should be soft and slightly crumbly.

Turn the dough onto a lightly floured surface and gently knead it just until it comes together. Shape it into a log about 2 inches in diameter, wrap in plastic wrap, and refrigerate for at least 2 hours.

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

Remove the chilled dough and slice it into ⅛-inch rounds, spacing them 1 inch apart on the prepared sheets.

Bake for 16-18 minutes until the edges are golden brown. Watch closely to prevent overbaking.

Carefully transfer the cookies to a wire rack to cool completely.