Preheat the oven to 350 F. Grease cake pans and line the bottoms with parchment paper rounds. Set aside.

In a medium bowl, combine the flour, sugar, baking powder, baking soda, and salt. Add the butter and beat until combined.

Add the eggs, one at a time, beating after each addition. Add the sour cream and beat until smooth.

Add the milk and vanilla extract and beat on medium speed for 1-1 ½ minutes.

In a separate medium bowl, whisk together the cocoa powder and hot water. Add half of the cake batter to the bowl and beat until combined.

Scoop spoonfuls of the two batters into each prepared cake pan, varying their placement in the pan. Aim to have equal amounts of vanilla and chocolate batter. Use a knife to swirl the two batters together and make the marble pattern.

Bake for 30-40 minutes or until a toothpick inserted in the center of each cake comes out clean.

Cool 10 minutes in the pan before transferring cakes to a wire rack to cool completely.

Place the melted butter in a medium bowl and whisk in the black cocoa powder.

Alternately add the powdered sugar and milk and beat until combined and spreadable. Add additional milk if needed.

Stir in the vanilla extract.

Transfer frosting to a large piping bag.

If desired, wrap your cake board in aluminium foil. Place on top of a cake decorating turntable, overturned bowl or plate.

Use a serrated knife to trim the top of each cake so that all of the tops are level.

Place one of the 6-inch cakes, cut side up, on the cake board. Pipe frosting on the top of the cake and then smooth into an even layer using the off-set spatula.

Place the second six-inch cake, cut side down, on top of the first cake. Pipe frosting on the top of the cake and then smooth into an even layer using the off-set spatula.

Pipe lines of frosting around the sides of the cake and then smooth into an even layer using the off-set spatula.

Place the 4-inch cake on an overturned bowl or plate. Pipe frosting on the top of the cake and then smooth into an even layer using the off-set spatula. Pipe lines of frosting around the sides of the cake and then smooth into an even layer using the off-set spatula.

Place the cakes into the refrigerator to chill for 10-15 minutes.

On a surface lightly dusted with powdered sugar, roll out the fondant to ¼ inch thickness using a fondant roller or rolling pin.

Using a Mickey ghost shaped cookie cutter or a paper template and a sharp knife, cut out the Mickey Boo shapes. Place the cut out shapes on a piece of wax paper.

Draw eyes onto each Mickey Boo using a black food-safe marker. Set aside until ready to decorate.

Remove the cakes from the refrigerator. Using a clean off-set spatula, gently smooth the sides of the cakes in small strokes to give the cake a matte feathered texture.

Place the 4-inch cake on top of the 6-inch cake, directly in the center of the cake.

Press the Mickey Boos into the side of the cake, placing them every few inches.

Place the jumbo marshmallows in a microwave safe bowl.

Microwave for 30 seconds or until the marshmallows puff and lose their shape.

Stir until the marshmallows are deflated and let them cool slightly.

Put on the food-safe gloves and spray your hands lightly with cooking spray.

Dip your hands into the marshmallow and stretch the marshmallow until it’s thin and web-like.

Wrap the strands around the cake, repeating until the cake is covered.

Let stand until the marshmallows are firm, about 10 minutes.