Preheat the oven to 400°F. Line a muffin pan with cupcake liners. Sift together 2 cups of flour, 1 cup of sugar, baking powder, and 1/2 teaspoon of salt in a large bowl, then set the mixture aside.
Whisk the eggs in a medium bowl until smooth. Add 1/2 cup of melted butter, milk, and vanilla, whisking until combined. Stir the egg mixture into the dry ingredients until just incorporated, ensuring the batter remains lumpy. Fold in the blueberries.
Prepare the streusel topping by combining 1/4 cup of flour, 2 tablespoons of brown sugar, 2 tablespoons of granulated sugar, cinnamon, and 1/8 teaspoon of salt in a medium bowl. Cut in the butter using a pastry cutter until the mixture is coarse and crumbly.
Fill the prepared muffin cups with batter and top each with approximately 1 tablespoon of streusel. Bake for 18 to 22 minutes, or until a toothpick inserted into the center comes out clean. Let the muffins cool on a rack for several minutes before removing them from the pan. Cool completely and store in an airtight container for up to 4 days.
