Preheat oven to 180 degrees celsius fan-forced (200 if using conventional).
Line a 12 hole muffin tin with paper muffin cases (see tips below).
Sift the self raising flour into a large bowl. Add the caster sugar and stir together. Create a well in the centre.
In a separate bowl, whisk together the egg, oil and milk.
Pour the liquid into the well and very gently fold the mixture together (the batter should be slightly lumpy - do not over-mix).
Very gently fold through the blueberries (do not over-mix).
Spoon the mixture into the muffin cases (fill ⅔ to the top).
Sprinkle each muffin with raw sugar (optional).
Bake for 20-25 minutes or until lightly golden.
Allow to cool in the baking tray for 5 minutes before transferring to a wire rack to cool completely.