Preheat the oven to 375 or gas mark 5. Grease or line muffin pan.
Remove 2 tablespoons of flour and set aside. In a bowl whisk together the remaining flour, salt and baking powder and save for later.
In a stand mixer with paddle attachment on medium high speed cream the butter with the sugar and brown sugar. Do not add the turbinado sugar that this step it will be used at the end. Once the mixture is pale and light add the eggs, one at a time, beating for a minute after each addition the add the vanilla.
Reduce the speed to slow and add half of the flour mixture and mix until just incorporated. Add the milk and buttermilk and mix until just incorporated and finish with the rest of the flour mixture.
Remove 1/2 cup blueberries and place in a mixing bowl, and crush with a fork, and mix into the batter. Toss the remainder of the blueberries the remaining 2 tablespoons of flour and fold into the batter.
Fill the greased/lined muffin pan with the batter and sprinkle the tablespoon of turbinado sugar over the tops of the muffins, and bake about 30 minutes. Or until a toothpick or knife inserted comes out clean. (It can have some blueberry reside on it)
Remove muffins from tin and cool at least 30 minutes.