Grease a box mould (approx. 1 1⁄4 l capacity; approx. 26 cm length) and sprinkle with sugar. Coarsely chop the walnuts and dark chocolate and preheat the oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see
Mix eggs, sugar, vanilla sugar and oil with the whisk of the mixer for about 3 minutes. Peel the bananas and weigh 300 g pulp. Cut into fine slices and fold into the dough. Mix flour, baking powder, 1 pinch of salt and cinnamon and stir in alternately with the milk briefly.
Then fold in the chopped nuts and chocolate pieces.
Smooth the dough in the form. Bake in the oven for about 1 1⁄4 hours. Cover with aluminium foil after about 30 minutes. Take out the cake and let it cool down in the tin for about 20 minutes. Turn out of the tin and let it cool down.