Preheat the oven to 180°C or 356°F.
Start by melting the coconut oil and allow to cool for a few minutes.
In the meantime, make the oat flour by mixing 1.5 cup (150g) in your food processor. Blend for about a minute until you obtain a powder.
Add all the other dry ingredients to your blender: 1/2 cup (50g) chestnut flour, 2 tsp. baking powder, 2 tbsp. coconut sugar if using, and blend until all ingredients are combined. If using maple syrup, add it with the wet ingredients in the next step.
Now add the wet ingredients, except for the blueberries: the 2-3 mashed bananas, 3 tbsp. melted coconut oil, 1/4 cup (50ml) milk, and 2 eggs.
Blend for a few seconds until all ingredients are combined (don’t over blend).
Fold in 1 cup of the blueberries.
Transfer to a silicon loaf pan (if using a steel pan make sure to oil it well or fill it with parchment paper first).
Add the remaining blueberries on top (about 1/2 cup), gently pushing them half into the batter.
Bake for about 30-35 minutes (the shorter, the moister)
Enjoy with a dollop of coconut yoghurt or Greek yoghurt and a spoon of almond butter.
Store leftovers covered in the fridge for up to 5 days, or freeze for up to 3 months.