For the Chocolate Banana Bundt Cake, in a bowl, mix the flour with the pudding powder or starch, cocoa powder, baking powder, baking soda and the chopped chocolate.
In another mixing bowl, beat the softened butter together with the salt, sugar and vanilla sugar until creamy. Then add the eggs and continue to beat vigorously (about 1 minute per egg).
Now add the mashed bananas and yogurt and continue beating briefly. Finally, add the flour mixture and mix until the flour is mixed with the wet ingredients (either with a wooden spoon or mixer on lowest speed).
Take x-any mold, grease it well, and pour the batter into the mold. Put the cake in the preheated oven at 160 degrees Celsius convection, or 180 degrees Celsius top/bottom heat for about 45 minutes (at 40 minutes, check if the cake is already done, as the time can vary from oven to oven).
After the cake is done, turn off the oven and let it rest in the closed oven for 5 minutes. Remove from oven and either let cool in the pan and then turn out, or turn the chocolate banana gugelhupf out of the pan immediately.