Preheat your oven to 180ºC/160ºC Fan and prep your 10" cast iron skillet if need be.
Cream together your unsalted butter and both light brown and granulated sugars until smooth and creamy.
Add in the beaten eggs, vanilla bean extract, plain flour, bicarbonate of soda, baking powder, and sea salt and beat briefly until smooth. It won't take long at all! (I use my Kitchenaid with the paddle attachment!)
Fold through your chocolate chips and spread onto the bottom of your skillet. I'd recommend using a treated cast iron skillet!
Bake in the oven for 30-40 minutes! (30 minutes will lead to a lovely gooey cookie, but more towards 40 minutes will be more baked through and solid - be careful though because some ovens may mean it needs longer in the oven anyway!)
Remove the cookie from the oven CAREFULLY as the skillet will be EXTREMELY hot! Leave to cool slightly before eating, and enjoy!
Notes
You can obviously swap out the chocolate chips for a mixture of flavours, but I used all milk chocolate as its my favourite. I wouldn't use more than 300g as it might not bake properly!
Serve with a scoop of icecream, some extra chocolate chips, and a drizzle of chocolate sauce!