Preheat the oven to 350°F degrees.
Melt the butter in a microwave-safe bowl. Allow the melted butter to cool down.
In a large mixing bowl, whisk together cooled, melted butter and both sugars until smooth and incorporated. Add in the eggs, pumpkin, and vanilla extract and mix until combined.
Add the flour, pumpkin pie spice, sea salt, and baking soda. Mix until just combined.
Pour in most of the chocolate chips (reserve a small amount for the topping). Fold in the chocolate chips until well distributed. The batter will be thick and sticky.
Coat an 8-inch cast-iron skillet with butter. Press dough evenly into the skillet, spreading it all the way to the edges. Top evenly with the reserved chocolate chips.
Bake for 24 to 28 minutes. (If you want it gooier, lean toward the shorter time.) *No matter how long you bake it, you will need to lay a piece of foil over the top of the skillet during the last 10 minutes of baking to avoid over-browning.
Remove from oven and sprinkle with sea salt, if desired. Enjoy the cookie warm, straight out of the skillet with vanilla ice cream, or allow to cool down for 30 minutes, then slice and serve. Enjoy!