Preheat oven to 180c.
In a jug or small bowl, combine buttermilk, vegetable oil, vanilla, melted butter and beaten egg then whisk to combine and set aside (the mixture will look curdled, that's normal).
250 ml buttermilk, 60 g salted butter, 1 egg, 4 tablespoon vegetable oil, 3 teaspoon vanilla extract
In a large bowl place self-raising flour and raw caster sugar and whisk together to combine.
375 g self-raising (self-rising) flour, 220 g raw caster sugar
Add the buttermilk mixture to the flour mixture then fold gently until it's just incorporated - it's important not to overmix.
Line a 12-hole muffin pan with muffin cases then divide the muffin batter evenly between each hole.
Bake for 20 - 25 minutes or until a skewer or toothpick inserted into the centre of a muffin comes out clean.
Remove the muffins from the pan and place on a wire rack to cool.