Preheat oven to 215c/ 425f . Line a muffin tin with 10-12 white paper muffin cases.
In a large bowl whisk together the dry ingredients- flour, caster sugar, light brown sugar, and baking powder. Once the ingredients are whisked well, gently fold in 280g of raspberries (saving a few for the topping) and white chocolate chips taking care to not burst the raspberries.
In a medium bowl whisk the butter, oil, eggs, sour cream, vanilla extract and milk. Whisk well to combine.
Pour the wet ingredients into the dry ingredients and use a spatula or wooden spoon to gently mix together. Be very careful to mix until just combined so as not to over activate the gluten in the flour.
Use a spoon or ice cream scoop to fill the muffin cases with the batter. Fill the cases to the top. That will ensure you get those tall and fluffy muffin tops.
Place a few of the reserved raspberries and white chocolate chips on top of each muffin and sprinkle with the Demerara sugar.
Bake for 20-25 minutes, until the edges of the muffins are golden and a tooth pick in the centre comes out with only a couple of moist crumbs.
Allow the muffins to cool for about 10 minutes in the muffin tin before transferring to a wire rack to continue cooling. When the muffins are slightly warm is the perfect time to eat them! Serve with a small smear of butter.