Preheat the oven to 375?F (190?C) and grease the muffin tin.

In a large bowl, whisk together the flour, sugar, baking powder, and salt.

In another bowl, mix the melted butter, milk, eggs, and vanilla extract.

Pour the wet ingredients into the dry ingredients and stir until just combined. Gently fold in the blueberries.

In a small bowl, combine the flour, brown sugar, butter, and cinnamon. Use a fork or your fingers to mix until crumbly.

Spoon the muffin batter into the prepared muffin tin, filling each cup about 2/3 full.

Sprinkle the streusel topping evenly over each muffin.

Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean.

Allow to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.