Preheat oven to 350 F degrees. In a mixing bowl add butter, sugar and brown sugar; mix until light and fluffy, about 3-5 minutes. Add egg and vanilla to the butter/sugar mixture and blend until combined. Add in flour, baking powder, baking soda, cinnamon and salt. Blend until flour is just incorporated and gently stir in oatmeal and chocolate chips
Scoop cookie dough into a lightly greased 8 inch cast iron skillet. Smooth out the top, making it even all around and bake in the oven for about 20 minutes or until golden brown and done. Serve with ice cream and enjoy