• Preheat the oven to 350 degrees Fahrenheit and grease two 9-inch round cake pans with nonstick cooking spray. Set aside.

Mix the Cake:

• In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder and salt.
  
• In a separate bowl, combine the eggs, coffee, buttermilk, oil, and vanilla.
  
• Slowly pour the dry ingredients into the wet ingredients and mix to combine. The batter will be thin. Add the black food color gel and mix well until well blended.
  
• Divide the batter evenly between the two prepared cake pans. Bake the cakes for about 25 minutes or until a cake tester or wooden skewer inserted in the center of the cake comes out clean.
  
• Remove from the oven and allow the cakes to cool in the pans for about 15 minutes. To remove the cakes from the pans, run a knife around the edges of the cake and invert. Place the cakes on a wire rack and allow them to cool completely before assembling.
  

Make the Frosting:

• In a large bowl, mix together the melted butter and black cocoa powder. Alternately, add powdered sugar and milk and mix until the mixture reaches a frosting consistency. Stir in the vanilla and food coloring. Mix well.
  

Assemble, Make Marshmallow Web and Decorate:

• To assemble the cake, with the help of a serrated knife or cake leveler, remove the domes from the top of the cool cakes so that they’re flat. Place one layer on a plate or cake stand and cover the top with some of the frosting. Spread evenly with an offset spatula.
Add the second layer of cake and top with frosting. Spread evenly on the top and sides of the cake. Prepare the marshmallow web.
  
• Place the marshmallows in a large microwave-safe mixing bowl. Melt the marshmallows in the microwave for about 30 seconds or until they start to lose their shape. Stir with a spatula. Allow the mixture to cool slightly.
  
• Using gloves for easy clean up, dip your fingers into the warm melted marshmallow mixture and stretch until thin and web-like. Wrap the marshmallow around the cake. Let stand until firm, about 10 minutes.
  
• Decorate the cake by placing a pile of candy (sixlets or malt balls) on the top. You can add more marshmallow web if desired. Decorate with a few spiders.