Preparation

• Preheat oven to 275 degrees; set a rack on a baking sheet and place in oven. Preheat waffle iron according to manufacturers instructions.
  In a medium bowl, whisk together flour, sugar, baking powder, baking soda, and salt; set aside. In a large bowl whisk together buttermilk, butter, and eggs. Add flour mixture to buttermilk mixture and stir just until batter is combined; fold blueberries into batter.
  Lightly coat waffle iron with cooking spray. Pour 1 cup batter (this may vary depending on size of waffle iron) in the center of iron, spreading evenly with a spatula. Close iron; cook until waffles are golden brown and crisp, 7 to 8 minutes.
  Remove from iron and transfer to rack in oven; repeat with remaining batter. Serve with blueberries, creme fraiche, and a sprinkle of confectioners' sugar.