Preheat oven to 400°f/200°C. If using the fan/convection setting, preheat oven to 375℉/190℃. Line a 6 cup jumbo muffin pan with high walled paper cups or grease and flour. You can also use a 12 cup muffin pan.
In a medium bowl combine all purpose flour, baking powder, baking soda and salt. Mix together well and set aside.
*All ingredients should be at room temperature* In a large bowl cream together unsalted butter and sugar until light and fluffy, 2-3 minutes. If your butter is very soft you can do this by hand. You can also use an electric mixer. Add eggs, one at a time, beating well after each addition. Add sour cream, oil, milk and vanilla. Mix until well combined.
Add about ¼ of the dry ingredients and mix until almost combined. Add the remaining dry mixture in 2 or 3 more stages. Mix until dry mixture is only half incorporated.
Reserve 15-20 blueberries for decorating on top (this is optional) and set aside. Add the remaining blueberries to the batter and fold until everything is incorporated. Do not over mix. The batter should be fairly thick.
Divide the batter among the 6 (or 12 if using) baking cups. There should be enough batter to make them very full. They will grow but they should not over flow. Decorate each muffin with some of the reserved blueberries, if you are doing this. Sprinkle each one with Turbinado sugar. Bake for 25-30 minutes for 6 jumbo muffins, 18-22 minutes for 12 regular muffins. Test with toothpick to see if batter comes out clean.
Cool muffins in the pan on a wire rack for 10 minutes before removing. Cool completely or serve warm.