Step 1

Preheat the oven to 350 degrees F (175 degrees C).

Step 2

Whisk flour, oats, baking soda, cinnamon, and salt together in a medium bowl.

Step 3

Cream white sugar, butter, brown sugar, and shortening in the bowl of a stand mixer until light and fluffy, 3 to 5 minutes. Add eggs, 1 at a time, mixing after each addition until fully incorporated. Mix in vanilla extract. Gradually mix in dry ingredients until combined. Stir in chocolate chips and pecans.

Step 4

Transfer dough to a well seasoned 10-inch cast iron skillet. Press down with your fingers to distribute evenly over the bottom of the skillet.

Step 5

Bake in the preheated oven until top is firm to the touch and edges have started to pull away from the sides of the skillet, 35 to 40 minutes.

Step 6

Remove from the oven and let cool for about 15 to 20 minutes. Run a spatula around the edges, lifting the cookie slightly as you go around. Carefully invert cookie onto a cutting board and then invert again onto a serving platter.