Beat the butter with the sugar, vanilla sugar and salt until frothy. Then stir in the eggs one by one and mix in the water. Mash the bananas and stir into the mixture. Then stir in the flour, baking powder and chocolate shavings.
Pour the batter into a greased bundt cake tin.
Bake the cake at 180 degrees (160 degrees circulating air) on the middle rack for about 60 minutes (stick test).
Let it cool down in the tin, then turn it out and cover it with chocolate icing or just dust with powdered sugar