1. Put the butter pieces in small saucepan and set over medium heat. Stir with wooden spoon until melted, 1 to 2 minutes. Using the pot holder, remove the pan from the heat and set it aside to cool.
2. Preheat the oven to 375 degrees F. Put paper liners in 12 muffin cups.
3. In medium mixing bowl, combine the flour, 1/2 cup sugar, baking powder, and salt. Mix with table fork.
4. In small mixing bowl, combine the milk, egg, and vanilla. Using the same fork, beat until well blended.
5. Add milk mixture, melted butter, and blueberries to the flour mixture. Using the rubber spatula, stir gently until ingredients are just blended.
6. Spoon equal amounts of batter into the muffin cups. Sprinkle the 2 teaspoons sugar evenly over the tops.
7. Bake the muffins until they are golden and have risen nicely, 18 to 20 minutes. To test, insert the toothpick into center of a muffin. If it comes out clean the muffins are ready. Using oven mitts, remove the muffin pan from the oven and lace it on the cooling rack. Let the muffins cool for at least 15 minutes before removing them from the pan. Gently turn the pan over, letting the muffins fall out onto the rack.