Heat the oven to 180°C. Grease and line a medium loaf tin.
In a large mixing bowl, mash the bananas with a fork, then add the oats and cinnamon. Combine and let it rest.
In another bowl, whisk the eggs with the sugar and vanilla. Add the oil and milk, then gently combine.
Add the flour, baking powder and salt to the banana mixture and gently combine. Add the egg mixture and combine until you get a sticky batter.
Chop the walnuts and chocolate into tiny pieces, then fold these into the batter.
Tip the batter into the prepared tin, spread it out evenly.
Bake the loaf in the middle of the oven for 40-45 minutes. After 20 minutes you can cover the tin with foil, if the top is already browning. After 40 minutes poke the cake with a skewer - if it comes out clean, it’s done - if not, bake it for another 5 minutes or so.
When the banana-bread is done, take the tin out of the oven.
Rest the loaf the tin for 5 minutes, then move it to a wire rack. Let it cool completely before slicing it.