Preheat your oven to 325°F (165°C) and prepare an 8x8-inch baking pan by lining it with parchment paper.

Cream together the softened unsalted butter and granulated sugar until light and fluffy, about 2-3 minutes. Incorporate the vanilla extract and kosher salt, then gradually add the all-purpose flour.

Transfer the dough into the prepared baking pan and press it evenly into the corners. Cover with plastic wrap and flatten with your hands for a smooth finish.

Using a fork, prick the dough about 36 times to allow steam to escape. Chill in the refrigerator for 30 minutes or in the freezer for 15 minutes.

Bake the biscuits for 30-35 minutes until the edges turn golden brown, keeping an eye on them.

Allow the biscuits to cool in the pan for about 5 minutes, then cut into rectangles while still warm.

Let the biscuits cool completely on a wire rack before serving. Enjoy with tea or coffee.