Preheat the oven to 390°F (200°C) and spray a muffin tray with non-stick spray.
Sift the all purpose flour into a mixing bowl and add the white and brown sugar, baking powder, baking soda and salt.
Mix up the homemade buttermilk by adding 1 Tbsp of lemon juice to a measuring jug and then adding room temperature milk up to the 1 cup (240ml) line. Let it curdle into buttermilk.
Add eggs, melted butter, oil and vanilla extract to the buttermilk and whisk the wet ingredients together until combined.
Pour the wet ingredients in with the dry and mix into a thick batter. Be very careful not to overmix.
Add 1 and 1/2 cups (187g) fresh blueberries to the batter and fold them in.
Divide the batter evenly among the muffin partitions on your prepared muffin tray. Top the muffins with the remaining 1/2 cup (63g) of fresh blueberries.
Place them into the oven and bake at 390°F for 5 minutes. Then turn the temperature down to 350°F and bake for a further 15 minutes until lightly browned on top and a toothpick inserted into one of the muffins comes out clean.
Allow the muffins to cool in the tray for a few minutes before removing them and placing them onto a wire cooling rack to cool completely.