This Midnight Chocolate Blackout Cake with Dark Chocolate Spider Webs is the perfect spooky cake to make for Halloween! It's super moist, filled with rich dark chocolate flavor, and it';s covered in a thick dark chocolate ganache frosting. The dark chocolate spider webs and spun sugar cobweb topping add a fun, festive touch!
Preheat oven to 350℉. Grease and flour two 8'' cake pans and line the bottoms with parchment paper. Set aside.
In a medium mixing bowl, combine the flour, cocoa powder, baking powder, baking soda, espresso powder, and salt. Whisk to combine and set aside. In a large mixing bowl, combine the eggs, brown sugar, and granulated sugar and whisk until smooth. Add the vanilla, vegetable oil, butter, melted and cooled chocolate, sour cream, and buttermilk and whisk until just combined.
Add the dry ingredients to the wet and mix with a rubber spatula until just combined. Pour the batter evenly into the pans and smooth out the tops with a spatula. Bake for 30-35 minutes or until a toothpick inserted comes out clean. Let the cakes cool for 10 minutes, then remove them from the pans and let cool the rest of the way on a cooling rack.
Place your chopped chocolate in a medium heatproof bowl. In a medium saucepan, combine the heavy cream, corn syrup, butter, and vanilla and heat over medium heat until butter is melted and mixture just begins to bubble around the edges. Pour cream mixture over the chocolate and let sit for 5 minutes. After the 5 minutes, stir mixture until the chocolate is smooth and silky. Refrigerate for 30 minutes. Add cooled mixture to the bowl of your stand mixer and whip with the whisk attachment for 4-5 minutes on medium-high speed until light and fluffy.
Melt the chocolate over a double boiler, or melt it in the microwave in 30-second increments, stirring in between, until melted. Be sure not to overheat the chocolate, or it will seize up! Let the chocolate cool for 10 minutes or so, then add melted chocolate to a piping bag with a very fine tip or ziplock bag with a tiny piece of the corner cut off. Place a sheet of parchment on a cutting board and pipe spider webs (you can use a stencil if you want, but it's not necessary!). Place in the freezer or fridge for 15 minutes or so or until set!
Place a small bowl or ramekin upside down over a cooking rack, with a piece of parchment underneath (this will ensure you don't get hardened sugar on your countertop!) Place sugar, water, and corn syrup in a medium saucepan and heat over medium heat. Simmer, stirring frequently, until mixture thickens and reaches a pale golden color. Let cool for 10 minutes, or until mixture forms threads when you drizzle it with a fork.
To test to see if the syrup is ready, dip a fork into it and drizzle the sugar mixture quickly in a circular pattern across the bottom of your bowl or ramekin, repeating several times to create a cobweb "nest". Gently pick up the cobweb off of the bowl, and set it aside. Repeat until you have your desired amount of cobwebs! If at any point the mixture gets too thick, place it back on the stove over medium heat for a minute or two to loosen up.
To assemble the cake, place one layer on a serving plate, and spread the top with the whipped chocolate ganache frosting. Top with another layer and spread top with frosting, leaving a little bit left for the sides of the cake. Use the leftover buttercream to "half" frost the sides, to create a "semi-naked" effect. Use an offset spatula or bench scraper to smooth out the sides of the cake. Press the dark chocolate spider webs onto the sides of the cake, and place the spun sugar cobwebs on top. Cut into slices and serve!
*Cake is best made and consumed day of, as the ganache frosting can harden too much if left out. If you want to make the layers ahead, they can be made 1 day ahead and wrapped tightly.
*Spun sugar cobwebs are very sensitive to humidity, so if you make them ahead of time, store them in an airtight container in a cool, dry place.