Preheat oven to 220ºC (200ºC fan forced). Spray a 20 x 10cm loaf tin with oil; line base and sides with non-stick baking paper.
Reserve one whole banana for presentation and mash remaining 3 bananas in a large bowl (1½ cups mashed).
Add sugar, milk and eggs and mix with a fork until well combined.
Sift flours and cinnamon on top of banana mixture, returning husks from the sieve to the bowl. Mix ingredients together until just combined, taking care not to over-mix, then gently fold through blueberries.
Spoon mixture into prepared loaf tin and smooth the surface. Slice remaining banana thinly and overlap slices through the centre of the loaf.
Bake for 35-40 minutes then cover with foil and bake for a further 20 minutes. Centre of loaf will remain moist but not wet when tested with a skewer. Allow to cool in tin for 5 minutes then turn onto a wire rack.
Cut into 1 cm slices and toast before serving, if desired.
LiveLighter ® State of Western Australia 2018. Reproduced with permission. For more healthy recipes and tips, visit www.livelighter.com.au