Preheat the oven to 180C/350F/gas mark 4. Grease an approx 11.5 x 21.5 cm / 4.5 x 8.5 in loaf tin and line with a strip of baking parchment.
Whisk together the mashed bananas, sunflower oil, milk, vinegar, brown sugar and vanilla extract in a large bowl.
In a separate bowl, sift together the flour, buckwheat/wholemeal flour, baking powder, bicarbonate of soda, cinnamon and salt.
Tip the dry ingredients into the wet and fold together until smooth. Fold in the chocolate chips.
Pour the batter into the prepared tin and spread level. Bake for about 60 minutes until firm to the touch and a skewer inserted into the centre comes out clean. Loosely cover the top with tin foil halfway through baking if it starts to brown too much.
Leave the banana bread to cool in the tin for 20 minutes then carefully turn it out onto a wire rack to cool completely.
If you are making the blueberry glaze then sift the icing sugar into a small bowl and stir in the freeze dried blueberry powder. Gradually stir in enough milk to make a thick but pourable glaze. Drizzle the glaze over the top of the cooled loaf and top with some banana chips. Store in an airtight container.