Preheat the oven at 175ºC/350ºF conventional oven and grease a 21,5 x 11,5 cm /8,5x4,5 inch loaf pan lined with parchment paper.
In a large bowl, add the all-purpose flour, granulated sugar, baking powder, cinnamon and salt. Give it a stir with a hand whisk to make sure everything has been combined.
240 g all-purpose flour, 200 g granulated sugar, 2 teaspoon baking powder, 1 teaspoon baking soda, 1 teaspoon ground cinnamon, ½ teaspoon salt
On a plate, mash the bananas until there are no banana chunks left. Add it to the bowl together with whole milk, vegetable oil, egg, and vanilla extract. With the hand whisk, whisk it all together until combined.
300 g banana, 60 g whole milk, 70 g vegetable oil, 1 large egg, 2 teaspoon vanilla extract
Chop the dark chocolate and add it to the batter. Gentle fold it into batter with a rubber spatula.
100 g semi-sweet dark chocolate bar
Pour the cake batter into the prepared loaf pan and take a butter knife and insert it into the top of the batter in the loaf pan and run it a straight line down the middle of the batter. Bake it for 1 hour 5-15 minutes. If the banana bread starts to brown too much on top, you can lightly cover it with aluminium foil to prevent further browning.
Let the cake cool on a cooling rack. After 10 minutes, gently remove the cake from the cake tin and let it cool down completely.