Preheat oven to 350°F (180°C) and line the bottom of a 9-inch cake pan with parchment paper and grease the sides.

In a medium sized bowl, combine the flour, cocoa powder, baking soda and salt. Set aside.

Add the butter and sugars to a large mixer bowl and beat together until light in color and fluffy in texture, about 2-3 minutes. Do not skimp on the creaming time.

Add the egg and vanilla extract and mix until well combined.

Add the dry ingredients to the butter mixture and beat just until combined. Use your spatula to gently finish combining everything to keep from over mixing the cookie dough.

Fold in the chocolate chips and candy corn. The cookie dough will be thick.

Spread the dough evenly into the prepared cake pan. Press a few more chocolate chips and candy corn into the top of the cookie cake, if desired.

Bake for 18-20 minutes or until it looks baked, but still wiggles a little when you jiggle it.

Remove from oven and allow to cool completely in the cake pan, then transfer to a serving plate.

To make the buttercream, add the butter to a large mixer bowl and beat until well combined and smooth.

Add about half of the powdered sugar and mix until well combined and smooth.

Add the vanilla extract and a tablespoon of cream and mix until well combined and smooth.

Add the rest of the powdered sugar and mix until smooth. Add more cream to get the right consistency.

Divide the buttercream evenly between two bowls. Color one with orange gel icing color and the other with yellow gel icing color.

To make the two-toned frosting, add each color of frosting to a Ziplock bag. Lay a piece of clear wrap out on the counter. Trim the corner off of each Ziplock bag. Pipe a thick row of each color of frosting side-by-side onto the clear wrap.

Fold the clear wrap over into a long log. Twist both ends closed and trim off one end so that the frosting is right at the edge.

Put the log into a piping bag with the open end of the log going into the piping tip. I used piping tip Ateco 844. Pipe swirls of frosting around the outer edge of the cake. Decorate with additional candy corn and chocolate chips, if desired.

Store cookie cake in an airtight container at room temperature for up to 48 hours, in the fridge for 3-4 days or in the freezer for up to 3 months. Cookie cake is best if eaten within 3-4 days.