1. Preheat your oven to 350°F (175°C). Lightly grease a 9-10 inch cast iron skillet or a similar oven-safe pan. If you prefer to make individual large cookies in a skillet, you can also use smaller individual cast iron dishes.

2. In a large mixing bowl, beat the 8 tablespoons of room temperature unsalted butter with ¾ cup granulated sugar until light and fluffy, about 2-3 minutes using an electric mixer. Scrape down the sides of the bowl as needed.

3. Beat in the large egg until fully incorporated and the mixture is smooth and glossy. Don’t overmix at this stage.

4. In a separate medium bowl, whisk together the 1 ⅔ cup all-purpose flour, ½ teaspoon baking powder, ¼ teaspoon ground cinnamon, and ⅛ teaspoon salt until well combined.

5. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix; a few streaks of flour are okay. The dough will be soft.

6. In a shallow dish, combine ½ cup granulated sugar and 1 ½ tablespoon ground cinnamon for the signature snickerdoodle coating. Mix well.

7. Press the cookie dough evenly into the prepared skillet. Sprinkle the entire surface of the dough generously with the cinnamon sugar mixture. For an extra thick coating, you can gently pat it into the dough. If making individual cookies, roll each portion in the cinnamon sugar mixture before placing them in the skillet or on a baking sheet.

8. Bake for 20-25 minutes, or until the edges are golden brown and the center is set but still slightly soft. The exact baking time will depend on your oven and skillet size. A toothpick inserted into the center should come out with moist crumbs, not wet batter.

9. Remove the skillet from the oven and let the cookie cool in the skillet on a wire rack for at least 10-15 minutes before adding toppings. This allows it to set up and prevents it from being too crumbly.

10. While the cookie cools, in a medium bowl, combine 1 cup heavy cream, 1 tablespoon instant vanilla pudding mix (dry), 1 tablespoon powdered sugar, ¾ teaspoon ground cinnamon, and ¼ teaspoon vanilla extract. Using an electric mixer, beat on medium-high speed until stiff peaks form. Be careful not to overbeat, or it will curdle.

11. In a small microwave-safe bowl, combine 6 tablespoons white chocolate chips and ½ teaspoon vegetable oil. Microwave in 15-second intervals, stirring well after each, until smooth and melted. Be careful not to overheat.

12. Once the skillet cookie has cooled slightly, spoon generous dollops of the whipped pudding cream over the top. Drizzle with the melted white chocolate. Serve warm directly from the skillet with spoons, ideally with a scoop of vanilla bean ice cream!