Preheat the oven at 175 degrees Celsius.
Butter a squarish baking form at 25x 25 cm. Cover evenly the bread crumbles in the form.
Mix the eggs and the sugar for 3 minutes in a bowl.
Add the flour and the baking powder and stir together.
Pour the batter in the baking form and place in the middle of the oven for 35 minutes.
Take out the cake and let it cool down in room temperature.
Divide the cake in two layers.
Whip the whip cream and the vanilla sugar to a hard foam.
Grate the chocolate and mix it with the whip cream.
Pour half of the whip cream in another bowl and mix it together with the blueberries.
Pour evenly the blueberry mixture on the bottom layer of the cake. Place the top layer of the cake on top. Pour evenly the whip cream over and on the edges of the cake.
Cover the cake with the marzipan lid and press gently so it covers nicely all over the cake.
Decorate the cake with some cake toppings according to the occasion.
Place cold until serving time. Preferable over the night.