Mix sifted dry ingredients. Fold in blueberries. Add beaten liquid ingredients in a few swift strokes, just until dry ingredients are moistened. The mixing is held to an absolute minimum, a light stirring from 10-20 seconds, batter will be lumpy. The batter should not be mixed to the point of pouring, ribbon-like from the spoon, but should break into course globs. If the batter has been beaten too long, the gluten in the flour will develop and toughen the dough. Sprinkle muffins with a mixture of sugar and cinnamon prior to baking.
To bake, preheat oven to 400°F Grease bottoms only of medium size muffin cups, fill 2/3 full. Bake at once in a preheat 400F oven until golden brown, about 15-20 minutes. If muffins remain in tins a few moments after leaving the oven they will be easier to remove.