Preheat the oven to 180oc and place muffin cases in a 12 hole tin.
Mix the dry ingredients first so add the flour, bicarbonate of soda, 50g oats and the sugar into a large bowl and stir then leave a well in the middle.In a separate bowl, mash the bananas until soft then add to these the oil, buttermilk and egg whites and stir until combined.
Pour the wet ingredients into the well in the dry ingredients and stir quickly with a wooden spoon. Do not over mix even if the mixture appears a little lumpy.Add in the blueberries then gently stir once more.
Divide between the muffin cases filling each one quite high.
Mix a couple of tablespoons of oats with one tablespoon of the muscovado sugar and sprinkle onto the top of each muffin.
Place into the oven for around 18-20 minutes until the tops are golden and the muffin springs back when pressed.
Cool in the tray for five minutes before removing and placing on a wire rack. Can be eaten hot or cold.