Using a hand mixer and a large bowl or a stand mixer, first beat the butter so that it is softened. Add powdered sugar and beat it with the butter. Then add vanilla, continue to beat. Add salt and flour to the bowl and beat until well combined. Dough will be slightly crumbly. Press the dough together and wrap in plastic wrap. Refrigerate for 30 minutes.

While dough is chilling, place toasted hazelnuts in sandwich-sized ziplock bag, squeeze out air, and seal. Crush the hazelnuts with a meat tenderizer until most pieces are 2-3 mm in size. Another way to do this step is to manually chop them with a large knife. Set chopped hazelnuts aside.

Preheat oven to 325 degrees F.

Roll out chilled dough on a floured surface so that it is 1/3 inch thick. Lightly flour the top of the dough as your are rolling it out, as needed. If dough is still sticking to the rolling pin, place a sheet of plastic wrap between the dough and the rolling pin and roll it out this way.

Using a round cookie cutter or an inverted cup, cut out as many round cookie as your can. Transfer to a parchment lined baking sheet. Gather the scraps of dough, roll out, and repeat. Bake for 18-20 minutes, until edges are barely golden. Let cool for 15 minutes and work on melting the chocolate.

To melt the chocolate, heat coconut oil in a small saucepan on low heat. Add chocolate and mix with a spoon continually as it melts so it doesn't stick to the bottom of the pan. After 3 minutes of mixing, remove saucepan from heat and let chocolate melt completely (about 2 minutes or so). Let chocolate cool for 5 minutes.

Load the warm, melted chocolate into a sandwich-sized ziplock bag. Cut a 1 mm corner off from the ziplock bag with scissors. Drizzle cookies with chocolate and sprinkle with chopped hazelnuts. Let chocolate set for 10 minutes before serving or storing.