Preheat oven to 350 degrees F. Grease a 9x13 pan with nonstick cooking spray and set aside.
In a medium bowl, whisk together flour, baking soda, sea salt, and cocoa. Set aside.
With a mixer, cream butter and sugars together until smooth. Add in eggs, one at a time. Next, add in vanilla extract and mix until combined.
Gradually add flour mixture and beat until just combined. Stir in the chocolate chunks. Divide the dough in half. Press half of the dough into the prepared pan. Spread the Nutella over the dough. Top the Nutella evenly with the remaining cookie dough. It is ok if some of the Nutella peaks out, but try to cover it as much as possible. Sprinkle the cookie bars with sea salt.
Bake cookies for 30 minutes, or until cookie bars are set around the edges, but still a little soft in the center. Don't overbake. Remove from oven and cool on a cooling rack. Cut into squares and serve.