Preheat your oven to 180°C fan-forced and line a 6-hole muffin tray with large muffin cases.
In a large bowl, add the caster sugar, oil, eggs, milk, sour cream and vanilla. Whisk until smooth and combined.
Add the self-raising flour on top and gently whisk until just combined. Be careful not to overmix.
Fold through the frozen raspberries and chopped white chocolate.
Divide the batter evenly between the 6 muffin holes, filling them generously for that bakery-style height.
Top with the reserved raspberries, extra white chocolate if desired, and a sprinkle of caster sugar.
Bake for 25 minutes, or until golden brown and a skewer inserted into the centre comes out clean.
Allow to cool slightly before serving.
