Grease and line the loaf tin.
Preheat the oven at 180xb0C.
In a blender or mixer, blend the bananas, oil, milk, egg, yogurt, vanilla extract and sugar to a fine puree.
Scrape it out into a large bowl.
Sieve all the dry ingredients into this bowl (all purpose flour, whole wheat flour, salt, cinnamon, baking powder, baking soda, drinking chocolate).
Gently mix in the vinegar and chocolate chips until well incorporated and scrape this batter into the prepared loaf tin and bake for 40 minutes or until a tester comes out clean.
Cool in the tin for 10 minutes. Unmold the loaf and cool for further 15 minutes before slicing with a serrated knife.