Grease a 9X13" baking pan or line with parchment paper
Add eggs, oil, and sugar to a large mixing bowl and whisk until it’s fully combined. The mixture will form a thick paste.
Add flour, salt and cocoa powder to the bowl and stir until fully combined.
Pour 1/2 of the batter into the prepared baking pan
Make 3 rows of 4 cookies, evenly spaced apart, then pour remaining brownie batter over the top until cookies are covered.
Bake at 350 degrees for 30-35 minutes, taking them out when they still feel undercooked. The batter will be very fudgy when you put a toothpick into the middle. If baking in a metal pan, reduce baking time to 25-30 minutes.
Allow to cool on a wire rack for 30 minutes
Add orange food coloring to to the vanilla frosting until you get the desired color
Spread frosting across the top of the cooled brownies and cut into 12 individual brownies
How to Make Spiderwebs:
Draw circles with black gel: Using your black decorating gel, pipe a large circle around the edge of each frosted brownie. Then, pipe a medium circle inside the first one, and a small circle inside the second circle.
Create the web: Take a toothpick and, starting from the center, drag it outward through all the circles to the edge. Repeat around the brownie until it looks like a spiderweb.