Place a pie plate on a sheet of parchment paper and trace the outline of the bottom with a pencil. Set the parchment aside (traced side up) to use as a template for the hazelnut/dulce de leche disc.

In a stand mixer fitted with the paddle attachment, cream 1/2 cup softened butter, 1/2 cup granulated sugar, and 1/4 cup packed light brown sugar on medium speed for 2 minutes. Scrape down the bowl as needed.

Add 1 large egg and 1 1/4 teaspoons vanilla and mix on medium speed for 1 minute, until combined.

In a separate bowl, whisk together 1 1/2 cups all-purpose flour, 1/2 teaspoon salt, and 1/2 teaspoon baking soda. Add the dry ingredients to the wet ingredients and mix until just combined. Stir in 1/4 cup semi-sweet chocolate chips and 1/4 cup milk chocolate chips. Set the cookie dough aside.

Roll out the pastry for a single crust and line the pie plate. Trim the excess dough and flute the edges as desired. Cover the lined pie plate with plastic wrap and refrigerate while you make the filling disc.

Put the traced parchment paper on the counter with the pencil outline facing down so you can see the outline through the paper but the pencil marks are not on the topping. Spoon 3/4 cup chocolate hazelnut spread (Nutella) into the center of the parchment circle and spread it evenly to fill the traced outline.

Freeze the Nutella layer for 10 minutes. Remove from the freezer and evenly spread 3/4 cup dulce de leche over the frozen Nutella layer, covering the same traced area. Return the parchment to the freezer for another 15–20 minutes or until the layered disc is firm enough to peel cleanly from the parchment.

Preheat the oven to 350 degrees F.

Remove the frozen Nutella/dulce de leche disc from the freezer. Carefully peel the parchment away from the disc. Place the disc into the chilled pie crust with the dulce de leche side up (Nutella side down).

Spoon the prepared cookie dough over the disc and press it into a uniform layer that reaches the edges of the crust.

Bake at 350 degrees F for 25–35 minutes, or until the top is golden brown and the center is almost set (it should jiggle slightly but not be very liquid).

Remove the pie from the oven, sprinkle with sea salt flakes, and allow to cool for about 30 minutes before slicing. If you prefer, the pie can be served the next day—once cooled, cover securely with plastic wrap; no need to refrigerate.

Slice and serve with ice cream and optional hot fudge sauce and caramel sauce.