Preheat your oven to 180C / 350F / Gas mark 4 and prep you muffin tins with liners or lightly grease them.
In a large bowl mix the flour, baking soda and sugar together until well combined. Add in the oats and combine.
In another bowl of medium size, mash the bananas until smooth, stir in the buttermilk, olive oil and egg whites.
Add the wet ingredients to the bowl of dry ingredients and mix sparingly until the mixture is just combined.
Add the blueberries and just give the mixture one stir to combine them but no more.
Fill the cases 2/3rds full.
Take your extra tablespoons of light brown sugar and rolled oats mix in a small bowl and sprinkle on top of your unbaked muffins.
Pop them in the oven for 18-20 minutes.
Once baked take them out of the oven and allow them to cool in their tins for at least five minutes, then transfer them onto a cooling rack.
These do taste really good still warm but are also really nice cold. They will keep in an airtight tin for 3 days.