Begin by preheating your oven to 180C/160C fan/gas mark four and lining a 12-hole muffin tin with paper muffin cases.
Pour the flour and bicarbonate of soda into a large bowl.
Hold back one tablespoon of the sugar before mixing the remainder into the bowl and 50g of oats.
Make a well in the centre and in a separate bowl mash the bananas until they are almost smooth.
Stir the buttermilk, oil and egg whites together into the mashed banana until it is evenly combined.
Next, pour the liquid mixture into the well and stir together quickly and sparingly with a wooden spoon.
Mix until combined, but do not be tempted to overmix as it will change the texture of the muffin once cooked.
Tip the mixture into the blueberries and stir them in with just one stir before dividing the mixture between the muffin cases.
Sprinkle the tops of the muffins with some oats and the resort of the sugar before baking the muffins for 18 to 20 minutes, or until the muffins have risen and are dark golden brown in colour.
Allow the muffins to cool for five minutes in the tray before lifting them out onto a cooling rack.