In a bowl, mix the egg yolks, sugar and flour. In a pot, boil the milk. While beating the mixture vigorously, slowly add the milk and vanilla. You can use a mixer. Add the butter.
If the mixture seems too runny, add more flour. Stir until it thickens. In a special form with removable sides, pour the cream in evenly.
Place the second cake layer on top and pour some more of the cream on. Put the final layer on and pour a little more cream than for the previous layers. Put the cake in the refrigerator for an hour.
Grate the chocolate and cover the cake with it. Allow the cake to cool again for an hour. After an hour passes, the cake is ready for serving.