Preheat the Oven: Set the oven rack to the middle position. Heat to 325ºF (165ºC). Line an 8 by 8-inch baking pan with parchment paper with a 1-inch overhang on each side. Set aside.
Make the Dough: Using a stand or hand mixer fitted with a paddle attachment, mix the butter, sugar, vanilla, and salt on low speed to combine, then increase to medium speed. Mix until light and creamy, about 2 minutes. Scrape down the sides of the bowl. Add the flour and mix on low until a hydrated and crumbly dough is formed. Do not overmix.
Form the Dough: Add the dough to the prepared baking pan. Lightly press it down until it evenly fills the pan. Place a piece of plastic wrap on top, and use the bottom of a spatula to flatten the surface.
Prick and Chill: Use a fork to lightly prick the surface of the dough, about 36 times, evenly spaced. Cover and refrigerate for 30 minutes. Alternatively, freeze for a maximum of 15 minutes.
Bake: Bake until the surface and edges are golden brown, about 30 to 35 minutes.
Cut: Cool on a wire rack for 5 minutes. While the biscuits are still hot, use a sharp knife to cut them into rectangles of desired size. Optionally, sprinkle the surface with granulated sugar while warm, about 1 tablespoon.
Cool: Let it cool completely in the pan. Carefully lift the biscuits out using the parchment paper overhang. Re-slice the lines if needed to separate them.