Preheat oven to 325 degrees F. Line a 13x9" baking pan with foil, extending the sides of the foil over the edges of the pan. Spray the foil with cooking spray. Set aside.
In the bowl of a stand mixer, beat together the butter and sugar until creamy, about 2 minutes. Beat in the powdered sugar and vanilla until smooth. Lastly, add in the flour, one cup at a time, until combined and soft. Stir in the chocolate chips.
Spread HALF of the mixture into the bottom of the pan, pressing into an even layer. Bake for approximately 15 minutes. Remove from oven, but keep oven on.
Once the crust is golden, pour the salted caramel sauce evenly over the crust. In a small microwaveable bowl, add the Nutella and microwave for about 20 seconds or until pourable. Pour the Nutella over the caramel layer evenly. Using your fingers, break apart the remaining dough over the top of the Nutella layer, trying to cover as much of the Nutella and caramel as you can. Sprinkle the top liberally with sea salt. (NOTE: if you're using a salted caramel sauce, use less sea salt on top).
Bake for approx. 25-35 minutes or until the top is light golden brown and the center is just about set - a slight jiggle is okay. Let the bars cool completely before cutting into squares. I highly recommend letting them set overnight.