Brooklyn Blackout Cake - unsalted butter

Method

• First make the frosting as this requires several hours to cool.
• Blend the cornstarch with about one-third of the milk until smooth.
• Bring the remaining milk to a boil in a small nonstick saucepan with the sugar, corn syrup and cocoa, whisking until smooth.
• Add the cornstarch solution and bring to a boil, stirring constantly until you have a rich, thick custard.
• Remove from the heat and add the vanilla and butter, stirring until it melts.
• In a perfect world it should be silky smooth; if it seems lumpy, simply process it briefly in a food processor.
• Pour into a large bowl, cover the surface with plastic wrap, and set aside to cool.
• Give it a stir before using.
• Preheat the oven to 325F convection oven/375F conventional oven, and butter two 8-inch nonstick cake pans with removable bases, at least 2 inches deep.
• Cream the butter and sugar together in a food processor, then incorporate the eggs one at a time.
• Add the vanilla, scraping down the sides of the bowl as necessary.
• Sift together the dry ingredients, and add them half at a time to the creamed mixture.
• Finally add the milk with the motor running.
• Divide the mixture between the cake pans and smooth the surface of each.
• Bake for 3040 minutes until a skewer inserted into the center comes out clean.
• Run a knife around the sides of each cake and leave to cool.
• When the cakes are cold, remove the sides and slit each one in half using a bread knife.
• To make the blackout, process one of the top halves to crumbs in a food processorif possible, choose the one that has risen unevenly.
• To assemble the cake, spread one of the bases on the pan base with one quarter of the frosting, taking it almost to the rim.
• Sandwich with the second cake base and spread another quarter of the remaining frosting over the surface.
• Top with the remaining layer of cake and use the remaining frosting to coat the top and sides.
• To finish, liberally coat the whole thing with the cake crumbs.
• Chill the cake for a couple of hours and then cover with plastic wrap.
• Remove from the fridge 1530 minutes before eating.