Preheat oven to 375 degrees. Spray a 10" cast iron skillet with cooking oil and set aside.
In a medium bowl, add your brown and white sugar, and melted butter. Stir until incorporated.
Mix in your egg and vanilla extract and stir until blended.
Add your flour, baking soda, and salt to the butter/sugar/egg mixture and stir until just blended.
Stir in your chocolate chips, give it a good fold.
Scoop your chocolate chip mixture into the cast iron pan. Spread evenly with a spatula.
Bake for 20-25 minutes. Take out when you see the edges start to brown. Sprinkle sea salt on top (we used Pink Himalayan salt which we had on hand) Allow to cool completely (if you can wait) before slicing and serving.