1 cup unsalted butter, cubed & room temperature
1 cup packed light brown sugar
1 cup sugar
1 tablespoon vanilla extract
2 large eggs
2 1/4 cups flour
1/2 teaspoon baking soda
1/4 teaspoon kosher sea salt
1 cup semisweet chocolate chips
1 cup white chocolate chips
1/2 cup chocolate-hazelnut spread
Directions1. Preheat oven to 300°F. Add butter and both sugars to bowl of stand mixer; beat on medium speed for 5 minutes, until light and fluffy.
2. Add vanilla then reduce speed to medium-low. Add eggs, one at a time, beating until fully incorporated. Stop to scrape down bowl, then add flour, baking soda, and salt. Beat on medium-low speed to form a firm dough; fold in chocolate chips.
3. Press one-half of cookie dough into bottom of 10-inch cast iron skillet. Spread hazelnut spread evenly over dough, leaving a 1/2-inch margin around edge. Top with remaining cookie dough, making sure to spread dough to cover hazelnut spread; seal edges of cookie by pressing lightly.
4. Bake 25–35 minutes, until edges are golden brown, and top looks slightly under baked but firm to the touch. Remove skillet from oven and let cool 10 minutes before serving drizzled with ganache.