Preheat oven to 400ºF and line a standard 12 cup muffin tin with paper cups.
Mix butter and 1 ¼ sugar until light and soft. Add eggs, beating after each one. Add vanilla, then sift the flour, salt, and baking powder, into the creamed mixture alternately with the milk.
Mash ½ cup of the blueberries with a fork, and mix into the batter, and fold in remaining whole berries.
Sprinkle the tops of the muffins with sugar. Reduce heat and bake at 375ºF for about 30-35 minutes. Remove muffins from tin and let cool for at least 30 minutes.