Preheat your oven to 350°F (175°C). Lightly grease your cast-iron skillet with butter or non-stick spray to ensure the cookie doesn't stick and gets a golden crust.
In a large bowl, cream together the softened unsalted butter, brown sugar, and granulated sugar using an electric mixer or whisk until fluffy and light in color. Add the pumpkin puree and vanilla extract, mixing until fully combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, salt, cinnamon, and nutmeg. This ensures the spices and leavening agent are evenly distributed throughout the dough.
Gradually add the dry ingredients to the wet mixture, stirring gently with a spatula until just combined. Avoid overmixing to keep the cookie tender. Fold in the chocolate chips carefully, saving a few to sprinkle on top if you like.
Transfer the cookie dough into your prepared skillet, spreading it evenly. Sprinkle the reserved chocolate chips on top for extra melty goodness. Bake in the preheated oven for 25-30 minutes, or until the edges are golden brown and the center is set but still soft. Remember, the cookie will continue to firm up as it cools.
Allow the skillet cookie to cool for at least 10 minutes before slicing. Serve warm for a gooey, decadent treat. It’s fantastic on its own or topped with a scoop of vanilla ice cream for an indulgent finish.