In a large bowl using an electric hand mixer, or a stand mixer with the paddle attachment, cream together the butter, sugar, and brown sugar until it's light and fluffy.
Add the dry ingredients into the wet ingredients and mix on low speed (increase speed as needed) just until combined and no flour streaks remain in the dough.
Transfer the chocolate chip cookie dough to the prepared cast iron skillet and spread it out evenly. Bake for 25-35 minutes, or until the edges are golden brown and the center is slightly gooey but not raw & jiggly.