Cut the butter into cubes and place them in a mixer, with the salt, granulated sugar and vanilla extract.
Mix them until they blend, forming a cream.
Sift the flour, add it to the mixture and continue to mix until it has a crumby texture.
Place the dough on a lightly floured pastry board . The dough will be very soft and easily workable. Compact it, to make it smooth, then use your hands to flatten it.
Cover it with a plastic wrap and store it in the refrigerator, to harden for at least half an hour.
Afterwards, take the mixture from the fridge and cut it with a knife in 4 cylinder shapes of 3 cm diameter, then cover the rolls using plastic wrap and place them in the fridge again for 3 hours, so that the dough is compact enough.
After the three hours have passed, place each cylinder in granulated sugar, making sure that the surface is even.
Using a knife, divide the cylinders in discs of 2 cm thickness, then place the cookies on baking paper over a tray.
Bake them in a preheated oven at 200 degrees Celsius (392 F) for about 15 minutes, until they get light browned.
Remove them from the oven, then immediately place them on a rack, so that they keep their sandy texture.
You can decorate them with powdered sugar.
Cooking time varies depending on how thick you want them to be. Thinner biscuits need a few minutes less, while thicker biscuits will need a few minutes more.