Preheat oven to 350F and line a 9” iron skillet with baking paper.
In a large bowl, whisk the butter, sugar and vanilla until lght and creamy. Whisk in the egg until combined. Add the flour, baking soda and salt and mix all the dry ing into the wet until just combined. Fold in half of the choc chips and spoon half of the cookie dough onto the pan.
Melt the nutella in the microwave for 30 sec until thin in consistency.
Spread the Nutella on top of the cookie dough on the pan. Top with the remaining cookie dough and flatten evenly.
Bake for 25- 30 mins for a gooey cookie. For a set cookie, cover the top with aluminum foil after 30 mins and bake for additional 10 mins. 5 mins into doneness, add the remaining choco chip. Cool for 10 mins before serving.
If making cookie balls - bake for 12-15 mins only. Chill the dough first for 2 hours before baking.