Heat the oven to 175 C (350 F)

Melt the butter in a big pot (that can later contain all the ingredients)

If you choose to include a chocolate bar then melt it together with the butter

Remove the pot from the heat and stir in the sugar and vanilla sugar until dissolved

Add the eggs while whisking gently (you don't want a lot of air trapped in the mixture)

Mix in the flour and cocoa powder which you add it a little at a time to avoid lumps (best is to use a sieve/sifter)

Crush the gingerbread and fold it into the mixture

Take a 24 cm cake pan with removable bottom and grease it. Then add some crushed gingerbread so it sticks to the greased surface

Pour in the cake batter and bake for 17 min. If you use a smaller / larger pan you will need to adjust the time. The cake should be crisp on the edges and sticky in the middle

Let the cake cool, this version was especially good when served with vanilla icecream!