1. Preheat the oven to 350°F (180°C). Line two 8 inches (20cm) springform tins with baking parchment and grease lightly. Set aside. 

 

2. Add the black cocoa and hot water to a large bowl and mix until you get a thick paste. Add the milk and mix until well combined. Set aside.

 

3. Add the butter and sugar (or sugar and erythritol) to a large bowl and mix on high speed until light and fluffy. Add the eggs one after another and mix well after each addition. Add the vanilla extract and mix in. Mix the flour with instant espresso powder, baking powder, baking soda, and salt and add alternating with the cocoa mixture to the bowl and mix until combined. Divide the batter evenly between the baking tins and bake for 45-55 minutes or until a toothpick inserted into the center of each cake comes out clean. Take out of the oven and let cool down completely on a wire rack. When the cakes are cool, remove from the tins and peel of the baking parchment.

 

4. For the chocolate pudding filling take about 1/3 of the milk and add together with the sugar, cornstarch, vanilla extract, egg yolks, and salt to a small bowl and mix until the sugar and cornstarch are completely dissolved. Set aside. Add the remaining milk, heavy cream, and chopped chocolate to a large pot and heat up until the chocolate has melted. Bring to a boil while stirring constantly. As soon as you can see bubbles coming up add the cornstarch mixture – keep stirring until the pudding thickens and bubbles again. The consistency should be a very thick and creamy pudding. Add the butter and mix in. Remove from the heat and place a piece of plastic wrap right on top of the pudding to prevent the development of skin. Let cool down completely.

 

5. For the chocolate ganache frosting chop the chocolate and add to a heatproof bowl. Add the heavy cream to a small pot and bring to a boil. Pour the hot cream over the chopped chocolate and let sit for 2-3 minutes, then stir until well combined and smooth. Let cool down to room temperature – the ganache should have thickens quite a bit. Whisk the cooled ganache with a handheld mixer or in your kitchen machine on high speed until light and fluffy for about 3-4 minutes. Fill 1/3 of the cream into a piping bag with a large round tip and keep the rest for later.

 

6. To assemble the cake cut the two cake layers each into two evenly thick layers – if the cakes are domed too much, cut that part off first. Place a first cake layer on a serving plate. Pipe a ring of the chocolate ganache frosting on the outer edge of that cake layer – that will be the barrier for the chocolate pudding filling. Add about 1/3 of the chocolate pudding on top of the cake layer and smooth out – try to fill everything up to the ganache barrier. Place a cake layer on top and press down a bit. Repeat the procedure twice to get nice even layers of ganache, filling, and cake. Finish with the last cake layer. Spread a thin layer of ganache frosting over the cake to coat it completely. Smooth out the sides and top and place in the fridge for about 20 minutes, then coat with more ganache frosting – keep some for the decoration. Place the cake in the fridge for about 1 hour.

 

7. For the chocolate glaze add the chopped chocolate and heavy cream in a microwave-safe bowl and eat up gently in the microwave until the chocolate has melted completely. You can do that also over a pot with simmering water. Let the well mixed and smooth glaze cool down a bit, then decorate the cake with it by pouring it over the cake and letting it drip over the edges. Let cool down and harden. To finish the cake fill the remaining ganache frosting into a piping bag with a star tip and pipe swirls on top of the cake.