Preheat the oven to 350°F. Line two 13x9-inch baking sheets with parchment paper, set aside.
In the bowl of a stand mixer, or with a handheld mixer, cream together the softened butter and powdered sugar over medium speed for 5 minutes, scraping down the sides as needed. Mix in the vanilla extract.
In a medium mixing bowl, whisk together the flour, cornstarch, and salt.
Slowly mix in the dry ingredients into the butter mixture, scraping the sides down between each addition. The dough will be very soft.
Using a tablespoon sized cookie scoop, scoop the dough and roll into balls. Place onto the prepared baking sheet, about 1- 1 ½ inches apart (I bake 15 on each sheet).
Bake for 10-12 minutes, just until the edges are set but the cookie is still pale and not browning at all.
For a powdered sugar coating, place powdered sugar on a plate. When cookies are just out of the oven, carefully dip each one into the sugar. Place on a cooling rack and once completely cool, coat them all in a second round of powdered sugar.