Mix the egg yellow with the milk.
Mix the butter, flour, sugar and the cacao powder in a bowl. Add the milk and mix well to a pie dough.
Cover a pie form with a baking paper and roll out the dough so it evenly covers the bottom and the edges of the baking form.
Place the pie bottom in the fridge until later.
Preheat the oven at 180 degrees Celsius.
Mix the cream cheese with the heavy milk, 3 egg yellows, corn flour, sugar and vanilla sugar.
With an electrical mixer make a hard foam out of the 4 egg whites. Add it gently to the cheese mixture. And stir together.
Take out the pie bottom from the fridge and pour the batter in the pie form.
Place in the middle of the oven for approx. 40 minutes or until the surface has a nice golden color.
Take out the cake and let cool down for a few minutes.
Place a round oven grill on top of the cake and turn it upside down and let it rest like that for 10 minutes. This way you will have a nice pattern on the cake.
Turn back the cake so it stands on the pie bottom and let it cool down.