Preheat oven to 425 degrees. Line pans with 18 muffin cups.
In a large bowl, whisk together the flour, baking powder, baking soda and salt. In a separate bowl, whisk together the butter, sugar, eggs, buttermilk and vanilla.
Add the butter mixture to the flour mixture and fold with a spatula to combine. Add the blueberries and fold gently until mixed into the batter.
Fill each of the 18 muffin cups with about 1/4 cup of the batter.
Top each muffin with about 1/2 teaspoon of the coarse decorating sugar.
Bake at 425 degrees for 5 minutes. Rotate pans and reduce oven temperature to 375 degrees.
Bake for an additional 10 - 15 minutes, or until tops of muffins spring back when gently pressed with your finger.