Preheat the oven to 200 degrees C (392 degrees F).

Grease a 12-cup muffin pan or line with paper muffin cups.

In a large bowl, mix together the self-raising flour and white sugar.

In a separate bowl, whisk together the melted butter, vegetable oil, buttermilk (or yoghurt and milk mixture), and eggs.

Pour the wet ingredients into the dry ingredients and mix until just combined. Be careful not to overmix.

Gently fold in the fruit.

Spoon the batter into the prepared muffin cups, filling each about 2/3 full.

Bake for 15 minutes, or until the tops spring back when lightly pressed.

Let the muffins cool in the pan for a few minutes before transferring them to a wire rack to cool completely.