Cream the softened butter with the confectioner's sugar.
Add the all-purpose flour, cornstarch, vanilla extract, and salt. Blend to combine.
Spoon the batter into a piping bag that has been fitted with a large star tip. *Note- to make this task easier, place the piping bag into a tall glass. Fold the piping bag down and spoon the dough into the bag.
Use a pencil to outline 2" circles onto a parchment paper sheet.
Flip the parchment paper over so the cookie dough doesn't come into contact with the pencil lead, and place the parchment paper onto a baking sheet. *Note - to prevent the parchment from slipping or lifting as you pipe the whirls onto the paper, add a small touch of dough onto the corners of the cookie sheet and press the parchment paper onto the baking sheet.
Pipe rosettes within the circle template drawn on the parchment paper. *Note - to pipe the rosettes, apply even pressure to the piping bag squeezing gently but firmly. Working from the outside to the inside in a circular fashion.
Chill the piped rosettes in the refrigerator for at least 30 minutes.
Preheat oven to 375-degrees.
Bake the Viennese Whirls for 12-15 minutes or until the cookies are the faintest golden brown.
Remove to a baking rack to cool completely.
Once fully cooled, sprinkle each cookie with a dusting of confectioners’ sugar.