Preheat oven to 200 degrees celsius (180 if using fan-forced).
Line a 12 hole muffin tin with muffin cases.
Sift the self raising flour into a large bowl.
Add the sugar and stir together.
Create a well in the centre of the dry mixture.
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).
Gently fold through any add-ins.
Spoon the mixture into the muffin cases (fill ⅔ to the top).
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.