Preheat oven to 425 degrees. Line muffin tin with cupcake liners.
Using a couple of forks, combine 3 tablespoons of white sugar, 3 tablespoons of brown sugar, ⅓ cup flour, and 5 tablespoons of cold butter in a medium-sized bowl until it becomes crumbly.
Whisk together flour, baking powder, salt, and sugar in a large bowl.
In a separate bowl, whisk eggs, oil, buttermilk, vanilla, and melted butter. Pour liquid ingredients into flour mixture and blend until moistened.
Combine blueberries, flour, and sugar and fold into batter.
Spoon batter into 18 prepared muffin cups and sprinkle with topping. Bake for 18-20 minutes or until done.
Video
Notes
For best results:
use room temperature ingredients
fill muffin pans to almost the top of the tin
let the muffins sit in the pan for 5 minutes after baking before removing them
allow the muffins to cool completely on a wire rack.