How to make
Preheat the oven to 300°F (150 °C). Grease the bottom and sides of a form with a diameter of about 10″ (25 cm), then sprinkle a thick, even layer of cocoa.
Sift 3/4 cup cocoa in a bowl, mix it with hot water and allow it to cool. In another bowl, sift the flour and mix it with the baking soda and salt.
In a third bowl, beat the soft butter with a mixer and gradually add the sugar. Beat for about 5 minutes until the mixture becomes pale and creamy. In a separate bowl, beat the eggs lightly with a fork and add them, while beating constantly with the mixer, into the butter mixture.
Beating needs to happen at low speed. Add the vanilla. Combine the milk with cocoa separately. Add the flour to the butter mixture in 3 lots while alternating with the cocoa mixture. Beat everything on low speed until mixed.
From this mixture, you can separately bake 3, 4 or 5 cake layers. Baking time depends on their thickness. Baking a layer generally takes about 25 minutes, but it depends on your oven.
It is best to check to see if it's ready with a toothpick. Leave the finished cake layer to cool on a cooking grid and start baking the next one in the same clean and greased form.
To prepare the cream, boil the sugar into a syrup with the chocolate and cocoa, stirring constantly, to obtain a smooth mixture. While the syrup is still warm, add the egg yolks and mix well again, being careful not to cook the yolks. They need to become a smooth mixture along with the other products.
Allow the chocolate mixture to cool slightly. In a bowl, beat the softened butter and slowly pour in the cooled chocolate mixture a little at a time, in which you've also put the vanilla. Add the walnuts, that you've chopped and lightly toasted in a pan, to the cream.
Set aside a few walnuts to decorate the cake. Place the first cake layer in a tray, smear it with cream, do this for all 3 cake layers. Gently press each cake layer down. Leave enough cream to cover the cake on top. Finally, decorate it with walnuts and leave it for 1-2 hours at room temperature. Later, you can put it in the fridge.
It is best to serve the cake the next day to allow the cream and the layers to flavor.
