Coat a 12-well muffin pan with
non-stick cooking spray, or use
cupcake liners; set aside.
Preheat oven to 425°F; mix topping ingredients; set aside.
Whisk the flour, baking soda, baking powder, and salt together.
Mix butter, sugar, and brown sugar until smooth and creamy in a large mixing bowl.
Add eggs one at a time, mixing well; add buttermilk and vanilla extract until combined.
Add the dry ingredients; mix just until combined; gently fold in blueberries.
Fill each muffin liner/well with batter; spoon and press topping on each.
Bake 5 minutes at 425°F; without removing muffin pan from the oven, reduce oven temperature to 350°F; bake ~20 minutes more, until a toothpick inserted in the center of a muffin comes out clean.
