Preheat the oven to 400°F and line a muffin pan with paper liners. In a large mixing bowl, sift together the flour, granulated sugar, baking powder, and salt; set aside. In a separate bowl, whisk the eggs until smooth, then incorporate the melted butter, milk, and vanilla, whisking until fully combined. Gently stir the egg mixture into the dry ingredients, mixing just until a lumpy batter forms. Carefully fold in the prepared blueberries.

To make the streusel, combine the flour, brown sugar, granulated sugar, ground cinnamon, and salt in a medium bowl. Using a pastry cutter, cut in the cold butter until the mixture resembles coarse crumbs.

Divide the batter evenly among the lined muffin cups, then sprinkle each with approximately one tablespoon of streusel topping. Bake for 18 to 22 minutes, or until the centers spring back when lightly pressed. Allow the muffins to cool on a wire rack for a few minutes before removing them from the pan. Once cooled completely, store in an airtight container for up to four days.