Preheat the oven to 350 degrees F. Spray two muffin tins with nonstick spray, or line the muffin cups with paper liners.
Combine the flour, baking powder and sugar in a large bowl; Use a pastry blender to cut in the butter until the mixture is crumbly. If you don't have a pastry blender, you can use two knives to cut the mixture together. Reserve 1 cup of the sugar/flour mixture in a small bowl and set aside.
Add the eggs, milk and vanilla to the remaining mixture. Use an electric mixer to beat at medium speed until smooth. Use a rubber spatula to gently fold in the blueberries.
Scoop the batter into the prepared muffin cups.
Drizzle the melted butter over the reserved 1 cup sugar mixture, stirring just slightly. Sprinkle over the muffin batter.
Bake for 20 to 25 minutes.
Notes
Use jumbo-sized muffin tins to make 12 large-sized muffins!