Lightly grease an 8-inch skillet with a little butter. Preheat the oven to 320 Fahrenheit.
In a large mixing bowl, combine ½ cup softened unsalted butter, ½ cup granulated sugar, and ½ cup light brown sugar. Using an electric mixer, beat for 1-2 minutes until pale and creamy.
Add 1 large egg and 1 teaspoon vanilla extract. Mix until combined. Add 1 ½ cups all-purpose flour and ½ teaspoon baking soda and gently fold it into the batter using a spatula or wooden spoon.
Stir in ½ cup chocolate chips,
Divide the cookie dough into two and place half of the dough into the prepared skillet. Press down to form one even layer. Then, spread ½ cup Nutella on top using a small spatula, ensuring you leave a small gap around the edges.
Grab small pieces of your remaining cookie dough, flatten them in your hand, and place them on top of the Nutella. Ensure all the cookie dough pieces join together and the layer of Nutella is completely covered.
Bake for 25 minutes or until golden brown. Let the cookie cool for a 10-15 minutes before serving.