Light, fluffy muffin recipe. Using oil, instead of butter, prevents the gluten in the flour from developing. Feel free to use frozen blueberries (do not thaw) instead of fresh but you may need to cook them longer. Adapted from Joy of Baking.
Preheat oven to 375f, grease or line muffin tins, 12 regular, 6 extra large.
Combine flour, sugar, baking powder, baking soda and salt in large bowl. Toss blueberries in flour mixture. In separate bowl combine buttermilk, egg, oil and vanilla extract.
Create a well/crater in the center of the flour mixture, pour the buttermilk mixture into the well/crater. Fold gently, just till ingredients are moist. More mixing will result in tough, chewy muffins.
Spoon batter into muffin tins, filling 2/3 (or more) full. Muffins have a nice crisp top, however, if you'd like a crunchy top, sprinkle with sugar, orange zest mixture.
Bake on centre rack for 20 mins, perhaps longer if using frozen blueberries. Muffins are done when toothpick inserted in center comes out clean. Let cool 5 minutes. Store in sealed container.