For the vanilla layer, beat the eggs with the sugar for about 10 minutes. Gradually add the flour and vanilla and whisk for at least another 5 minutes. Pour the mixture into a cake form with a diameter of about 10″ (26 cm), covered with baking paper, and lightly greased. Bake it in a moderate oven for 20-25 min and after the sponge cake cools slightly, cut it in two with a thread.
Similarly, make the cocoa layer, but only one this time. Blend the flour for the cream with cold milk, beat the egg yolks and add them to the milk and flour. In a thick enameled bowl, mix this egg mixture with the remaining milk and stir until the cream thickens. When it thickens well, remove from the heat, stir until cool and add the vanilla.
Separately, beat the butter with powdered sugar into a fluffy cream and add the butter mixture into the cooled vanilla cream. Take a third of the cream and add walnuts to it, which you've ground or finely crushed.
Stick the cake layers together with the cream, while spreading the walnut cream on the second layer. Smear the top of the cake and make decorations as you like.