Preheat the oven to 350 degrees. Lightly grease the cast iron skillet with softened butter.

Mix the oats, flour, baking soda, and salt in a small bowl and set it aside. Melt the butter. Add this with the sugar in a medium-sized bowl. Mix them well. To this, add the egg and vanilla. At this point, only mix to incorporate.

Top tip: Make sure not to overmix the batter after the eggs are added. This will result in a tough cookie, and that is not what you want, trust me!

After the eggs and vanilla are mixed in, add the flour mixture and mix this in as well. Be careful not to overmix. Last is the chocolate chips. Mix them in. Add the batter to your cast iron pan and place it in the preheated oven.

This cookie will bake in 20-25 minutes, in my oven it is always 20. You do not want to overbake this, it should be slightly soft in the center. Once it is done, remove it from the oven.

It can be served warm or let it cool. While I think this is sweet enough already, you can also top it with a few scoops of ice cream before serving.