Preheat the oven to 375º F (180º C). Line a square cake pan of about 7.87 inches (20 cm) with parchment paper.
In a big bowl, using an electric mixer, cream together the butter, confectioners sugar and vanilla extract for 2 minutes until you get a soft, creamy mixture.
Add in the sifted flour, hazelnuts and salt. Mix using a rubber spatula until all the ingredients are fully integrated and a soft dough forms.
Put the dough in the cake pan and flatten it to even it out (you will cut the bars once baked). Bake at 375º F (º80º C) for about 15 to 20 minutes until slightly golden brown.
Take out of the oven and let it cool down for 10 minutes in the cake pan.
Meanwhile, to melt the chocolate, put it in pieces in a plate and melt in the microwave heating in 30 seconds intervals, meaning, you put it in for 30 seconds, then take it out and mix using a fork. You repeat this process until the chocolate is completely melted. This will keep it from burning.
Spread the melted chocolate on top of the cookie and even it out. Refrigerate for at least 30 minutes. Cut the cookie into square pieces to make the bars.
For more recipes go to www.hornomx.com