How to Make It
Preheat the oven to 350°. Line 2 baking sheets with parchment paper. In a large bowl, with an electric mixer, cream the butter with 1/2 cup of the confectioners' sugar at medium-high speed until pale and fluffy, about 1 minute. Add the egg yolks, vanilla extract and salt and beat at medium-high speed until blended, scraping down the sides of the bowl as needed. Beat in the flour and ground hazelnuts at medium speed until just incorporated. Cover the dough with plastic wrap and refrigerate until firm, at least 30 minutes.
Using about 1 1/2 tablespoons of the dough for each cookie, roll the dough into 3-inch-long cylinders with tapered ends. Form the cookies into crescents and transfer them to the prepared baking sheets, spacing them 1 inch apart. Bake the cookies for 18 minutes, or until light golden. Remove from the oven and let the cookies cool on the baking sheets for 10 minutes, or until just cool enough to handle.
Spread the remaining 1/2 cup of confectioners' sugar in a shallow bowl. Dip each warm cookie in the confectioners' sugar and coat evenly. Transfer the cookies to wire racks and let cool completely.