Prepare the dough:
In a medium-sized bowl, whisk together the flour, cornstarch, and salt. Set aside. Using an electric mixer, beat the butter and powdered sugar together on medium speed until light and fluffy.
Add the vanilla and flour mixture:
Mix in the vanilla extract, then gradually add the flour mixture, continuing to mix until well incorporated.
Shape the dough:
Divide the dough into 2-3 equal portions. Roll each portion into a 1-inch diameter log on a piece of plastic wrap. Twist the ends of the plastic wrap tightly to enclose the dough, making sure it’s airtight. Refrigerate for at least one hour until firm.
Slice and chill:
Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper. Slice the dough into 1/2-inch thick bites and place them on the prepared baking sheet, leaving about 1 inch of space between each cookie. Chill in the refrigerator for at least 30 minutes before baking.
Bake:
Bake the cookies in the preheated oven for 8-10 minutes, or until the edges are lightly golden brown. Remove from the oven and let them cool completely on the baking sheet.
Finish with powdered sugar:
Once the cookies are cooled, sprinkle powdered sugar on top. Alternatively, you can roll the slightly cooled cookies in powdered sugar to fully coat them.
Store:
Place the cookies in an airtight container, layering them between sheets of wax paper. These cookies will keep well for about 2 weeks.