Preheat the oven to 350 degrees F. Spray a 9 or 10 inch cast iron skillet with nonstick spray.
In a large bowl, use an electric mixer to combine the butter with the sugars until creamy and light, about 2 to 3 minutes. Mix in the egg and vanilla.
In a separate bowl, whisk together the flour, oats, baking powder, baking soda and salt. Add the dry ingredients to the wet ingredients and mix until combined. Stir in the chocolate chips.
Scrape the cookie dough into the prepared skillet and pat it into an even layer (damp hands or hands sprayed with cooking spray helps with this). Bake 25 minutes, or until cookie dough is set. Remove from the oven and let the cookies cool for at least 20 minutes.
Cut and serve warm, or wait to cut later. Serve slices topped with vanilla ice cream, if desired.