In a large mixing bowl, whisk together flour, hazelnut flour, and salt until well blended.
In the bowl of an electric mixer using the paddle attachment, cream the butter, confectioners’ sugar and vanilla on medium speed until well blended.
On low speed, add dry ingredients and blend well.
Make sure all the dry ingredients are well incorporated even using your hands to mix the dough, if needed.
Wrap the dough in plastic wrap and chill it for one hour.
Line 2 sheet pans with parchment paper.
Using a dough cutter, divide the dough in half.
Divide each half of the dough into 8 equal pieces.
Using a 2 ½ inch round cookie cutter with 1 inch high sides, press 1 of the pieces of dough into the cutter pressing it in so that it forms a perfect circle.
Bring the cookie cutter with the dough inside onto 1 of the prepared sheet pans.
Using your hands, gently press the dough out of the cookie cutter onto a corner of the sheet pan.
Continue pressing the remaining pieces of dough into the cookie cutter and pressing it out onto both sheet pans spacing the circles out so that they do not touch.
Bake cookies for approximately 20-22 minutes or until cookies are barely light brown. Cool completely.
Make the Ganache Topping
In a medium saucepan bring the cream to a boil.
Remove pan from the heat and add chocolate chips.
Whisk the mixture until it becomes smooth and the chocolate is completely melted.
Pour the ganache into a medium heatproof bowl and allow it to cool to a pipeable consistency. To speed this process along place the bowl of ganache into the refrigerator for about 1 hour stirring the mixture every 15 minutes, or you can place the bowl of ganache over a bowl half filled with ice water whisking constantly until the ganache becomes thick.
To frost the shortbread: fill a piping bag fitted with a large star tip with some of the ganache.
Pipe a large rosette on the top of each shortbread. Refill the piping bag as necessary.
Allow the ganache to harden by chilling shortbread cookies in the refrigerator on the sheet pans.
Store in an airtight container separated by wax paper.