In a stand mixer fitted with a paddle attachment, cream the butter and sugar together, then add flour, corn flour, baking powder, and eggs. Mix until the batter is well mixed and smooth.
Preheat the oven to 350 degrees F. Transfer a baking sheet with parchment paper.
With a rolling pin covered in flour, roll out the dough on a floured work surface to ¼-inch thick.
Cut out the cookies using small, circular cookie cutters, and transfer to the prepared baking sheet, spacing the cookies about 1½ inches apart.
Sprinkle the cookies with the nonpareils and then bake for about 15 minutes.
When done, use a spatula to transfer the cookies to a wire rack to cool.
Flip half of the cookies and add 2 teaspoons of chocolate hazelnut spread. Top with the remaining cookies, and serve.