Step 1

Make the chocolate cakes:

Step 2

Preheat oven to 350 F.

Step 3

Butter and line baking pans with parchment paper.

Step 4

In a large mixing bowl, gently mix the butter, sugar, flour, cocoa powder, Greek yogurt, vanilla, eggs, baking powder, baking soda and salt.

Step 5

Once it comes together, add the boiling water and mix until smooth, making sure to scrape down the sides of the bowl.

Step 6

Pour the batter evenly into pans, then bake for 28 to 32 minutes.

Step 7

Cool cakes completely before assembling.

Step 8

Make the fudge frosting:

Step 9

In a medium-sized saucepan over medium heat, combine the butter, sugar, cocoa powder, chocolate and salt. Cook for 4 to 5 minutes, until it starts to bubble around the edges but isn't boiling.

Step 10

Slowly add the cream. The grainy texture will melt away, and you'll be left with a thick, glossy chocolate sauce. Stir in the vanilla.

Step 11

Cool completely, about 2 to 4 hours, before frosting a cake or you'll get a thin glaze instead of a frosted look.

Step 12

To cool the frosting quickly, place the warm frosting in a bowl, then place the bowl in a larger bowl of ice. Whisk until chilled.

Step 13

To assemble:

Step 14

Set one cake on a plate and top with half the frosting, smoothing it all the way to the cake's edge.

Step 15

Top frosted cake with the second cake. Spread remaining frosting over the top and add some swirls with a spoon or butter knife. Leave the sides of the cake unfrosted.

Step 16

Make the marshmallow spiderwebs:

Step 17

Place the marshmallows in a microwave-safe bowl and heat for 20 to 30 seconds.

Step 18

Pick up about 1/4 cup of the mixture with your fingers and gently knead by gently pressing your hands together and then spreading them apart to create long "webs."

Step 19

Lay the webs across the frosted cake and continue until desired webbyness is achieved. Decorate with candy corn, Halloween sprinkles, googly eyes or plastic spiders.