Preheat the oven to 350 degrees F and line a 9" inch square pan with parchment paper.
Spread the Nutella into the pan in an even layer and place in the freezer for at least 30 minutes.
Meanwhile, make the brownie batter. In a small bowl, add the semisweet chocolate and oil. Heat in the microwave in 30 second increments until fully melted. Set aside.
Meanwhile, in a large bowl, add the sugars, eggs, and vanilla. Using an electric mixer, beat on high speed for about 2-3 minutes until the mixture has doubled in size.
While mixing on low speed, slowly pour the chocolate, oil mixture into the sugar, egg mixture.
Next, add the flour, cocoa powders, and salt, and mix on low speed until fully combined.
Remove the frozen Nutella layer from the pan, and re-line it with parchment paper. Pour half of the brownie batter (weigh it for even layers) into the prepared pan and smooth it out with an offset spatula. Place the frozen layer of Nutella on top followed by the remaining brownie batter. Smooth out the top with an offset spatula.
Bake the brownies for about 34-36 minutes. Allow them to cool completely in the pan before removing.
Cut into 16 squares, and enjoy!