In a large bowl, beat the softened butter with an electric mixer until light and fluffy.
Gradually add the powdered sugar and beat until well combined and creamy.
In a separate bowl, whisk together the flour and salt.
Add the flour mixture to the butter mixture in three additions, alternating with the vanilla extract, mixing on low speed until just combined. Do not overmix.
Cover the dough and chill in the refrigerator for at least 30 minutes.
Preheat oven to 300°F (150°C). Line baking sheets with parchment paper.
Shape the dough into small balls (about 1 inch in diameter) and place them on the prepared baking sheets, about 2 inches apart.
Gently flatten each ball with the tines of a fork or the bottom of a glass.
Bake for 10-14 minutes, or until the edges are lightly golden. The cookies should still be pale.
Let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely.
Notes
These cookies can be decorated with sprinkles or a drizzle of melted chocolate after cooling.