Black Cocoa Sponge Cake

1. Preheat the oven to 165°C / 325°F and line two 6-inch round cake pans with parchment paper.
2. In a large bowl, sift together the flour, black cocoa powder, baking powder, baking soda, and salt, then set aside.
3. In another large bowl, whisk the eggs, sugar, oil, and vanilla until smooth. Gradually alternate adding the dry ingredients and the buttermilk-coffee mixture, gently stirring until the batter is smooth and slightly liquid.
4. Divide the batter evenly between the two prepared pans.
5. Bake in the center of the oven for 45-55 minutes until fully baked.
6. Let the cakes cool slightly, then remove from the pans and allow to cool completely on a wire rack. Once cooled, slice each cake into two layers for a total of four cake layers.

Ghost Meringues

1. Follow the French meringue recipe and transfer it into a piping bag fitted with a large round tip.
2. Preheat the oven to 100°C /212°F and pipe large meringue blobs onto a baking sheet lined with parchment paper.
3. Bake the meringues for about 1 hour, then let them cool in the turned-off oven with the door slightly open for another hour.
4. Melt some dark chocolate using a double boiler or microwave, and use a toothpick or fine brush to draw eyes and a mouth on the meringue ghosts.

Swiss Meringue Buttercream

1. In a heatproof bowl, mix the egg whites and sugar. Place the bowl over a double boiler and heat, whisking constantly, until it reaches 55°C/131°F (about 4 minutes).
2. Transfer the mixture to your stand mixer and whip at high speed for about 10 minutes until you have a firm, cooled meringue.
3. Gradually add the butter pieces and vanilla extract, mixing until smooth and creamy.
4. Divide the buttercream in half.
5. Leave one half white, and in the other, sift in black cocoa powder and add a few drops of black food coloring. Mix until evenly colored.

Mascarpone Whipped Cream

1. In a large bowl, combine all the ingredients: cold mascarpone, cold heavy cream, powdered sugar, and vanilla.
2. Whip with an electric mixer on low speed for about 2 minutes until the mixture is smooth and firm. Transfer the mascarpone whipped cream to a large piping bag.

Layer Cake Assembly

(Assemble the layer cake in a deep cake pan or use an adjustable cake ring for a straight build.)

1. Place the first layer of sponge cake in the ring or pan, lined with plastic wrap for easy removal. Pipe a border of white buttercream around the edge of the sponge, fill the center with mascarpone whipped cream, then add the second sponge layer. Repeat for all layers.
2. Chill the assembled cake in the fridge for 20-30 minutes. Carefully remove the cake from the mold and place it on a turntable with a cake board.
3. Cover the entire cake with a layer of white Swiss meringue buttercream to trap crumbs. Apply a slightly thicker layer to create a white visual effect when sliced. Smooth the buttercream with an offset spatula and cake scraper, then refrigerate for 20 minutes to set the buttercream.
4. Apply a new layer of black buttercream over the entire cake and smooth it using a cake scraper. Let the finished layer cake chill in the fridge for 1 hour.
5. Decorate with meringue ghosts on top and around the sides, adding eyes and other Halloween decorations.
6. Be sure to take the cake out 20-30 minutes before serving to soften the frosting and filling.