Ingredients
Method
Start by making the pastry cream for the cream diplomat
- In a medium sized heat safe bowl, whisk together the eggs and cornstarch. The mixture will be very thick and pasty. Set aside. In a large saucepan, whisk together the milk, sugar, and espresso powder. Bring the mixture to a simmer over medium heat. Once simmering, slowly stream ½ cup of the hot milk into the egg yolk mixture, stirring constantly. Then, slowly stream the egg yolks back into the remaining milk while whisking constantly. Let the mixture continue to cook on medium heat for 30 seconds, still stirring constantly. It will start to thicken very suddenly, but just keep stirring. Let the mixture cook untouched for 30 seconds, then stir for 30 seconds, and cook untouched for another 30 seconds. Remove the mixture from the heat and stir in the butter and vanilla. Let the custard cool in the pot for 10 minutes before stirring and transferring to a heat safe bowl. Cover the custard with cling wrap so that the cling wrap is touching the surface of the custard. Let the custard chill like this in the refrigerator for 3 hours.
Make the cake
- Preheat the oven to 350℉. Grease and line three 8 inch cake pans with butter and parchment paper. Then, grease the top of the parchment paper as well. Set aside.
- In a large mixing bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt. Set aside. In a medium sized mixing bowl, whisk together the vegetable oil, sour cream, eggs, milk, and vanilla extract until smooth. Pour this mixture into the dry ingredients and whisk until almost combined. Slowly stream the warm coffee into the batter, stirring constantly until you have a smooth batter. Finally, stir in the melted unsweetened chocolate until smooth and combined. The batter will be thick and a little glossy.
- Pour the batter evenly among the three pans and spread into an even layer. Bake the cakes for 24-27 minutes or until an inserted toothpick comes out clean and the cake is pulling away from the sides of the pan. Let the cakes cool completely in their pans set on a wire cooling rack.
Make the Oreo frosting
- In a food processor, pulse the Oreos into fine crumbs. Set aside.
- In a large mixing bowl using a hand or stand mixer fitted with a whisk attachment, whip the butter on medium high speed until glossy and lightened in color, around 3 minutes. Add in the sugar, vanilla extract, heavy cream, salt, and Oreo crumbs. Whip on low speed for 30 seconds before turning the speed up to high and whipping for 1 minute until fluffy and combined. Set aside while we finish the creme diplomat.
Finish the creme diplomat
- Once the custard has chilled, make the stabilized whipped cream. Place the cold water in a small bowl and sprinkle the gelatin on top. Let the mixture sit for 5 minutes, or until the gelatin absorbs the water and has solidified. Then microwave the mixture in 5 second increments until you are left with a thick, clear, syrupy mixture. Set aside to cool.
- In a large mixing bowl using a hand or stand mixer fitted with a whisk attachment, whip the cream on high speed to soft peaks. Soft peaks means when you lift the whisk out of the bowl, the cream should just barely hold it's shape. Turn the mixer down to low speed and very slowly stream in the cooled gelatin mixture (if it has thickened too much, microwave for 5 seconds). Then turn the speed up to high and whip to stiff peaks. Make sure you don't over whip this!
- Remove the custard from the fridge and whisk until smooth again. It will be very thick. Carefully fold the custard into the stabilized whipped cream until just combined.
Assemble
- If desired, level the cakes by slicing off the tops to create an even surface. Place one layer of the cake on your cake stand and spread a very thin layer of the Oreo frosting on top. Then, using a large circular piping tip, pipe a ring of frosting around the edge to act as a moat for the filling (see video). Fill the moat just bellow the top with the creme diplomat. Place the second cake layer on top and repeat this process. You will not end up using all of the creme diplomat. Place the final cake layer on top and cover the tops and sides with the Oreo frosting, spreading it as evenly and smoothly as possible. Reserve the remaining frosting for decoration.
- Place the cake in the freezer for 15 minutes or so while we make the chocolate frosting.
Make the chocolate frosting
- In a medium sized mixing bowl using either a hand or stand mixer fitted with a whisk attachment, whip the butter and shortening on medium high speed until light and fluffy. Add the confectioners sugar, cocoa powder, vanilla extract, black food coloring, and salt and whip on low speed for 30 seconds before turning up to high speed to whip for 1 minute.
Decorate
- Remove the cake from the freezer. Fill a piping bag fitted with a small round tip ( I used Wilton #4) with the chocolate frosting. Pipe a spider web design on the top of the cake (I recommend looking up a picture to make it easier.) Pipe different phases of the moon going around the sides of the cake. Use the remaining Oreo frosting and chocolate frosting to add extra frills on the top and bottom of the cake as pictured if desired. I used the piping tip #4B.
- Slice, serve, and enjoy! Cake stays fresh sealed in the refridgerator for up to 4 days.