Put the milk with the sugar and butter to boil, dilute the egg yolks with the flour and 2/5 cup (100 ml) milk and add them in a thin trickle to the boiling milk.
Stir until thickened, add the vanilla sugar and remove from the stove. Cover with foil to prevent a crust from forming. Put the water to boil and add the sugar.
Boil 3-4 min., add the vanilla sugar, remove from the stove and leave to cool slightly. Melt the chocolate in a water bath.
Put a cake layer in a suitable plate and syrup with 6-7 spoons of the syrup, leave for a minute to soak in and cover with cream. Place the 2nd layer and repeat.
Leave the homemade cake for 3-4 hours in the fridge to harden.