Preheat the oven to 350 degrees F. Grease a 12-cup muffin tin.
In a bowl, combine the flour, baking powder and sugar. In another bowl, combine butter, egg, and milk and mix well. Pour the wet ingredients into the flour mixture and with a spatula, stir until just combined. Do not beat or over mix; it's okay if there are lumps in the batter. Gently fold the blueberries into the batter.
Spoon the batter into the muffin tray, filling each cup about 2/3 full. Bake for 10 minutes and remove from the oven. Sprinkle the tops of the muffins with the granulated brown or white sugar and return the muffins to the oven to bake for an additional 10 to 15 minutes, until the tops are golden brown and a toothpick inserted into the center of a muffin comes out clean. Cool for about 10 minutes in the pan before turning the muffins out.