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

In a large mixing bowl, cream together the unsalted butter and granulated sugar using a hand mixer on medium speed until light and fluffy, about 2-3 minutes.

Add the vanilla extract and kosher salt, mixing until well combined. Gently fold in the all-purpose flour until just combined.

Transfer the dough to the lined baking pan and press it evenly into the pan to about ½ inch in thickness.

Using a fork, dock the surface of the dough with shallow pricks, then refrigerate for 30 minutes.

Bake in the preheated oven for 30-35 minutes until golden brown around the edges but slightly pale in the center.

Remove from the oven and let cool for 5 minutes, then cut into rectangles while still warm.

Allow biscuits to cool completely in the pan before using the parchment paper to lift them out.