Mix in a bowl the butter, sugar, eggs, vanilla sugar and salt. Blend thoroughly with a mixer at medium speed for about 5 minutes. Mix the melted chocolate and cocoa. Then add the sifted flour and baking powder, stir nice. Will be a mixture of dark brown color and consistency of very thick cream. If you feel you can add a little flour or milk, depending on the density. Divide the dough in the pan size 25x25, which have previously covered with baking paper. Level the surface with a wet spatula and bake desserts for about 30 minutes at 180C degrees. Then let cool and cut into two parts - to get two the base. Make the cream. Mix the butter with condensed milk and cocoa and mix until uniform. nice Beat eggs with sugar, add 1/2 cup milk, flour and let the mixture boil. When cool, mix with the combination of butter and condensed milk. If the consistency is too thick, pour milk. If you is very liquid, prepare the following mixture and add it to the cream (but do not make advance only if necessary): Boil 3 tbsp semolina in 1/2 cup milk. Cook until a very thick porridge and do not add any hot or warm to the cream in any case. Assemble the cake, sandwiched with both the base part of the resulting cream and brush with the remaining cake outside.