Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper or a Silpat mat.

Toast hazelnuts in a skillet over medium heat for about 5-7 minutes until fragrant. Let cool, then pulse in a food processor until finely ground.

In a medium bowl, whisk together the pulsed hazelnuts, all-purpose flour, and salt. Set aside.

In a stand mixer, beat the room-temperature butter and granulated sugar on medium-high speed until light and fluffy, about 3 minutes. Add vanilla extract and mix well. Gradually incorporate the dry ingredient mixture, mixing on medium speed until just combined.

Transfer the dough onto plastic wrap, press it into a ½-inch thick disk, and chill in the fridge for at least 1 hour or up to 3 days.

Roll out the chilled dough to about ¼-inch thickness on a floured surface. Cut out cookies using your preferred cutter.

Arrange the cookies on the lined baking sheets and chill in the fridge for an additional 30 minutes.

Bake in the preheated oven for 9-11 minutes, or until the edges are slightly golden and the tops appear pale.

Allow the cookies to cool completely on a wire rack. Once cool, pipe a generous amount of Nutella onto half of the cookies, then top them with the remaining cookies.

Dust the assembled cookies with confectioners’ sugar before serving.