Preheat your oven to 350°F (175°C). Lightly grease and flour a 9x5 inch loaf pan, tapping out any excess flour.

In a small bowl, combine the 1/4 cup flour, 1/4 cup light brown sugar, and 1/2 teaspoon ground cinnamon for the streusel topping. Add the cold, diced butter and use a pastry blender or your fingertips to cut it into the dry ingredients until coarse crumbs form. Set aside.

In a large mixing bowl, whisk together the 1 1/2 cups all-purpose flour, 1/2 cup granulated sugar, 2 teaspoons baking powder, and 1/2 teaspoon salt for the bread.

In a separate medium bowl, whisk together the 3/4 cup milk, large egg, 1/4 cup melted butter, and 1 teaspoon vanilla extract until well combined.

Pour the wet ingredients into the dry ingredients. Stir gently with a spatula just until everything is combined and no dry streaks of flour remain. Be careful not to overmix! Gently fold in the 1 cup of blueberries.

Pour the batter evenly into your prepared loaf pan. Sprinkle the streusel topping evenly over the top of the batter.

Bake for 50-60 minutes, or until a wooden skewer or toothpick inserted into the center of the loaf comes out clean. If the top starts to brown too quickly, you can loosely tent it with aluminum foil.

Let the bread cool in the pan on a wire rack for 10-15 minutes before carefully removing it from the pan. Allow it to cool completely on the wire rack before slicing and serving. This helps prevent it from crumbling.