Preheat the oven to 350 degrees F. Grease an 8 inch square glass pan and line bottom with a strip of parchment paper that covers the bottom and comes up over two opposite sides. Remaining two sides don’t need to be covered, just greased.
Melt the butter over medium low heat in a small saucepan. Add chopped chocolate and reduce heat to low. Stir until chocolate is melted and smooth, adding in the cocoa powder as you stir. When smooth, add the hazelnut oil and brown sugar and stir until it dissolves slightly, then remove from heat.
In a mixing bowl, using a hand-held electric mixer, beat the eggs for about 1 minute or until frothy. Gradually add the granulated sugar and continue beating for 5 minutes or until thick and frothy. Beat in the vanilla and the salt.
Fold the melted chocolate mixture into the egg mixture, then fold in the flour.
Pour the batter into the prepared pan, sprinkle nuts over the top, and bake in the center of the oven until set and starting to crack, about 30- 35 minutes.
Pull from oven and sprinkle chocolate chips over hot brownies so that they melt just enough to adhere.
Let cool completely at room temperature, then chill thoroughly. To remove from pan, loosen sides without parchment gently with a knife, then pull up on parchment and take brownies out of the pan. Cut into squares.