Mash the bananas in a bowl and then combine all the liquid ingredients (except the blueberries).
Mix the dry ingredients in a bowl.
Combine the liquid mixture with the dry ingredients with the help of a whisk.
Coat the blueberries with a pinch of flour before adding them to the muffin mixture. This will prevent them from sitting on the bottom of your muffins while baking.
Bake at 210°C (400°F) for the first 15 minutes, then lower the temperature to 180°C (350°F) for the remaining 25-30 minutes.