Mix the sugar, vanilla sugar, butter and eggs in a mixing bowl with a hand mixer. Then add the ingredients in the order given above, previously chopping the bananas in a bowl with a fork. Add a good shot of rum at the end. Pour the batter into a well-greased loaf pan. Bake for about 50 minutes. Remove the cake from the mold and spread the cake icing onto the cake according to the instructions on the packet. Decorate to your own taste (for example with brittle).