Mash the bananas in a bowl with a fork. Mix in the melted butter, yogurt, 1 egg and half of the sugar. Stir in 150 g flour, vanilla sugar and baking powder. Fold in the chocolate chips.
In a second bowl, mix together the cream cheese, egg, 50 g flour and remaining sugar and fold in the blueberries.
Butter a loaf pan and sprinkle with flour. Pour in the banana batter and smooth it out. Pour the cream cheese mixture on top and lightly marble everything with a fork.
Bake in the preheated oven for 40 - 50 minutes, possibly covering with aluminum foil so that the dough does not get too dark.
Let the tin cool down a little, turn the cake over, carefully turn it over and let it cool on a wire rack.