Recipe and Photo Source: http://littlesweetbaker.com/2015/02/13/bakery-style-blueberry-streusel-muffins/
Yield: 12 muffins
Preheat oven to 425 degrees. Place muffin liners in a muffin pan.
Prepare the streusel topping. Put the ingredients in a bowl and use a fork to mix until it resembles coarse crumbs.
In a large bowl, add the flour, baking powder, baking soda, and salt. Whisk to combine. Set aside.
In a medium bowl, add the melted butter and sugar. Whisk to combine. Add the eggs, milk, and vanilla. Whisk until smooth.
Add the wet ingredients to the dry ingredients. Gently stir with a rubber spatula and flour is incorporated. Gently fold in the blueberries.
Fill the muffin cups about 3/4 full. Top with streusel topping.
Bake for 5 minutes. Reduce the temperature to 375 and bake another 15 minutes or until a toothpick inserted in the middle comes out clean.