Preheat the oven to 220°C/430F fan and line a 12 cup muffin pan with cupcake liners. Keep aside 3 to 4 berries and chocolate chips to sprinkle on the top of the muffins before baking. Mix the cinnamon and raw sugar in a bowl and set aside.
In a large mixing bowl, whisk together the flour, cornstarch, baking powder, sugar and salt. Pour in the blueberries and white chocolate chips, and stir through gently using a silicone spatula or wooden spoon to coat the berries and chocolate with the flour mixture.
300 grams plain flour, 50 grams cornstarch, 150 grams white sugar, ½ teaspoon salt, 180 grams blueberries, 200 grams white chocolate chips, 3 teaspoons baking powder
In another mixing bowl, jug or saucepan, melt the butter. Allow the butter to cool before adding the rest of the wet ingredients. Whisk until well combined. Pour the wet ingredients into the dry and mix through until just combined.
125 grams butter, 2 eggs, 3 teaspoons vanilla extract, 125 grams Greek Yoghurt, 125 grams milk
Divide the muffin batter between the 12 cupcake liners, filling the liners to the top. Sprinkle the extra berries and chocolate over the tops of the muffins. Then sprinkle the tops of the muffins with the cinnamon sugar - about 1 to 1½ teaspoon per muffin.
½ teaspoon ground cinnamon, 3 tablespoons raw sugar
Bake the muffins at 220°C/430F for 5 minutes. Turn down the oven to 200°C/390F and bake for a further 12 to 15 minutes or until just baked. Allow the muffins to cool in the tin for 10 to 15 minutes before placing them on a wired cooling rack to cool completely.