Preheat the oven to 175 degrees. Line a mold of about 20 x 20 cm, with with parchment paper.
Melt the butter in a saucepan. Add sugar, cocoa, salt and vanilla sugar and mix.
Whisk in 1 egg at a time. Finish by whisking in the wheat flour and mixing together to form a smooth batter.
Distribute the batter evenly in the mold and bake in the middle of the oven for 20-22 minutes. Allow to cool.
When the cake is cool, add the ganache. Place the brownie in the fridge for a while for the chocolate ganache to solidify properly.