Preheat the oven to 300 degrees. Prepare two large cookie sheets with parchment paper.

In a large mixing bowl, cream together the butter and confectioners sugar until light and fluffy, about 5 minutes.

Whisk together the flour and cornstarch. Slowly add the flour mixture to the butter/sugar mixture, beating well after each addition.

With hands lightly dusted with the cornstarch, scoop the dough into 1-inch balls and roll until smooth. Place cookies 1-inch apart onto the cookie sheets. Press lightly with a fork dipped into cornstarch. Top with nonpareils.

Bake for 20 to 22 minutes. Cool on the baking sheets for 5 to 7 minutes before transferring to wire racks.