Preheat your oven to 350 °F (175 °C). Line 3 round 8" cake pans with parchment paper on the bottom and grease the sides.

In a large bowl, stir together the sugar, flour, Dutch-process cocoa, black cocoa powder, baking powder, baking soda and salt. Add eggs, milk, oil and vanilla.

Mix until combined, and then stir in the boiling water. The batter will be quite thin.

Divide the batter between the three pans. That’s 658 grams of batter per pan (675 grams per pan if using Bob's GF flour).

Bake for 24-28 minutes or until a toothpick comes out with some moist crumbs but no uncooked liquid.

Let cool for 10 minutes in the pans, and then turn out onto a rack to cool completely; about 2 hours. My cakes weren't flat, but not very rounded, either. If you want to, you can level them (I did not).

In a large mixing bowl, beat the cream cheese and butter together with an electric hand mixer at medium speed until well combined. It's okay if it looks a little crumbly.

Gradually beat in the powdered sugar until totally combined, and then beat in the vanilla and salt.

Beat in a little orange food coloring at a time until you're happy with the color.

Place the bottom layer of cake, rounded side down, on the serving dish.

Spread 1 1/4 cups (288 grams) of frosting over the bottom layer, almost until the edge.

Put on the next cake layer, rounded side down, and spread the same amount of frosting over the top.

Place the third cake layer on top, rounded side up.

Use 1/2 cup (115 grams) of frosting as a crumb coat. Keep the frosting refrigerated until ready to use. And if you ever think it's not firm enough, place it back in the fridge.

Spread it all around the cake.

Place the cake in the freezer for 20-30 minutes after putting on the crumb coat (or 1-2 hours in the fridge). You can also refrigerate it overnight to help break up the workload.

Then cover with the remaining frosting. Place the cake in the fridge for 4-8 hours, or overnight, so that it's as firm as possible. How long you need depends on if the cake layers were frozen and if/how long you chilled the frosting before and during the decorating process. With my very warm kitchen and not chilling the cake or the frosting, 4 hours was enough to firm it up. 8 hours would have been better for a cleaner slice.

Keep in mind that the marshmallow spiderweb can become wet and sticky over time, so it's best to serve the cake within a few hours of decorating for optimal taste and texture.

Place the mini marshmallows in a microwave-safe bowl. Microwave on high for about 30-60 seconds, or until the marshmallows are completely melted. Stir well to ensure the marshmallows are smooth and stretchy.

Allow the melted marshmallows to cool slightly, just until it's not too hot to handle but still stretchy.

Put on food-handling gloves, and take a small amount of the melted marshmallow between your fingers. Stretch the marshmallow between your fingers to create thin, web-like strands.

Gently pull the marshmallow strands across the surface of your frosted cake, wrapping it around the sides and across the top to create a spiderweb effect. You can layer the strands in a crisscross pattern to achieve a more realistic web look.

If the marshmallows start to harden, you can reheat them briefly in the microwave to regain the stretchiness.

You can use a toothpick or small tool to help adjust or refine the web strands on the cake if needed.

Add little plastic spiders. Be aware that they’ll stick to the marshmallow and pull some of it along with the frosting when removed.

To make slicing through the marshmallow easier, use a serrated knife with a little oil on it, then using a sawing motion to cut the cake.

If you want to make the cake elements in advance, let the layers cool, wrap the layers individually in plastic wrap and place inside a Ziploc bag. They can be stored at room temperature for up to 2 days, refrigerated for 3, or frozen for 3 months. No need to defrost before assembling the cake.

The frosting can be refrigerated for up to 4 days total or frozen for up to 3 months.

You can assemble the cake, add the crumb coat and frosting and then freeze it for up to a week. I would wrap it in plastic wrap and then place it in a big bag, just to be safe. The spiderweb should be added as close to serving as possible. If you have any leftovers, it's safe to refrigerate and freeze the cake with the spiderweb on it, but you probably won't want to serve it as it'll be a mess.