Line a 9” round cake pan with foil and spray with cooking spray.
Pour melted butter into an electric mixer fitted with paddle attachment. While still hot, add both sugars and mix on low until combined. Let sit to cool for a few minutes.
Turn mixer (with butter mixture bowl attached) on low. Add egg and mix completely. Mix in vanilla extract. Add baking soda, salt, and flour and mix until combined. Stir in 1 1/4 cups chocolate chips.
Press into prepared pan. Chill for 1-2 hours.
Preheat oven to 350°. Bake for about 20 minutes. The top will start to get golden, but it will still look a bit jiggly in the center. Cool completely.
When ready to top, melt remaining 1 cup chocolate chips with shortening (about 45-60 seconds in the microwave).
Spread over the top of the cookie. Add candy corn in desired pattern. Chill to set.