Preheat the oven to 350°F (180°C). Spray a 9x13 pan with non-stick spray and set aside.
In the bowl of a stand mixer or with an electric hand mixer, cream together the butter, brown sugar, and granulated sugar until light in color and fluffy in texture.
Scrape the sides and add in the egg and vanilla. Mix until well combined.
Next, you will add the flour, baking soda, and salt. Mix until a soft dough forms.
Once a soft dough has formed, press half of the dough into the bottom of the prepared pan.
Now, spread the Nutella onto the top of the cookie dough in the pan.
Crumble and press the remaining cookie dough onto the top of the Nutella layer.
Sprinkle the top with flakey sea salt.
Bake at 350°F (180°C) for 15-17 minutes. The edges should begin to turn brown but the entire top shouldn’t.
Allow the bars to cool completely before cutting and serving.
