On low mixer speed, cream butter and sugar until fluffy. Add eggs, one at a time, and mix until blended. Sift dry ingredients and add alternately with milk and vanilla. Mash 1/2 cup blueberries and stir in by hand. Add rest of blueberries whole and stir in by hand.
Grease muffin tins well with butter (grease top surface of tins as well). Pile mix high in each muffin cup. Sprinkle sugar over tops. Bake at 375° for 30 minutes. Cool in pan for at least 30 minutes.Makes about 1 dozen large muffins.